# Gas Pump Accuracy?



## cwsqbm (Aug 4, 2004)

woody underwood said:


> No, no no! You keep missing the point. The oil companies aren't keeping that 3/10s, someone is using it! And the gas in the hose just might be high test, so YOU have a chance of not getting ripped off and somebody has the chance of making out. So you get beat up by .20 cents every time you fill up (Maybe)....once a week = .20X52=$10.40...how can you argue about this? No, I don't like to get ripped off either, but I try and pick on something viable. As for getting 3/10 of my car...pro-rate that times 13 (gallons in a tank) X 52 (weeks in a year) and I''ll give you a ZHP hubcap next time you're in KC. Buy you a beer too!


Actually, wouldn't it be 3/10 x $.2 (the typical price difference around here for premium.

So, that's $.06 of value I loose every time I fill up, which has been running $38 recently (I don't take it to E). So, that means I'm potentially loosing 0.15% of my value. Damn! Where's my lawyer, this is an outrage! Of course, in my beater, I may actually gain some premium fuel, but I get no additional value because my truck doesn't run any better on premium than unleaded.

To get a better value, run your tank lower.


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## kc5 (Aug 9, 2004)

woody underwood said:


> No, no no! You keep missing the point. The oil companies aren't keeping that 3/10s, someone is using it! And the gas in the hose just might be high test, so YOU have a chance of not getting ripped off and somebody has the chance of making out. So you get beat up by .20 cents every time you fill up (Maybe)....once a week = .20X52=$10.40...how can you argue about this? No, I don't like to get ripped off either, but I try and pick on something viable. As for getting 3/10 of my car...pro-rate that times 13 (gallons in a tank) X 52 (weeks in a year) and I''ll give you a ZHP hubcap next time you're in KC. Buy you a beer too! Oh yeah, back when I was in high school pumping gas we used take turns filling up our cars out of the hoses after the station closed down. It was a big place, 30 pumps...so...30X3/10=9 gallons and it would keep a 53 Chevy running all week (Didn't really worry about whether it was regular or Ethyl either)


With all due respect, I'm always amazed that so many people no longer seem to care if they get ripped off by even a tiny amount. It's the principle to me.

The point here is not that someone is not using that 3/10s of a gallon. Instead, it's that (1) I'm not always getting what the pump says I paid for, and (2) gas stations are collecting more than they should. Further, it does not even out for the gas stations or me as plien69 suggests because there are more cars on the road that use regular gas than there are that require premium. The odds are greater that I will unwittingly get some regular gas than it is that a regular grade user will get some premium gas. I personally am out very little, but gas stations stand to make a lot of money when it's multiplied by millions of gallons over time.

Believe me, this does not keep me awake a night, I was just passing it along as a potential point of interest. Silly me for being principled. Besides, who knows, maybe Road & Track was wrong about the 3/10s -- then of course all this would be moot.

Woody, about that beer offer, how about a margarita instead?


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## lilmano1 (Jul 4, 2005)

I agree with you Jonathan. I never see the tankers coming to fill up more than one valve. Unless they have some underground filter-I think premium in the US probably means we can afford to spend more so we of the PREMIUM FOOLS.

As for your Rim search//how's that going? I recommend www.Superbuytires.com anyday.My 2002 745i Sterling Gray sport package looks wonderful on 22" Dolce-12
check the wheels out...


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## AzNMpower32 (Oct 23, 2005)

Is that why I managed to pump 17.85 gallons once into my X3...............which has a 17.7 gal tank?


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## plien69 (Apr 11, 2005)

I never said it evens out for you. I fully acknowledge that people who purchase premium are getting the short end. If that's a big enough deal for you, then buy a car that uses regular.

I did say that it evens out for the gas stations. Let's suppose all pumps are ultra accurate, and everyone gets exactly what they pay for. One person buys regular, one person buys premium. Then they swap 3/10 of a gallon after the fact. Isn't that what's happening now? The gas station doesn't make any more money. They still get $$$ for x gallons of regular + y gallons of premium, regardless of who pays for what fraction. 

If you really want ultra accurate pumps, then pump technology will need to be advanced, new pumps designed, purchased, and installed, and someone will have to pay for that. Guess who that will be? The consumer, in the form of higher gas prices. Fair? Perhaps not. But that's business, and that's reality.

No one likes to be taken advantage of, but there are reasonable limits to how fair we can make things. I drink my coffee black, why should I pay the same as someone who adds cream and sugar? My car weighs 2800 lbs, why should I pay the same highway toll as that 6000 lbs SUV? I ordered a Whopper with no pickles, why am I still paying full price? Because any solution to these inequities would overwhelm any savings if the situations were truly fair.


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## Penforhire (Dec 17, 2005)

Hmm, someone mentioned motorcycles above and that reminded me. I would know if my motorcycle fill amount was off by 1/3rd of a gallon (might even notice 1/4 gallon) based on very consistent mileage and a physical fill-to-the-brim process (seems to vary by about +/- 0.1 gallon).

I have to say I've never noticed any rip-off and I've had to fill up in dozens of stations in So Cal. Maybe it is a regional problem but not around here?


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## kc5 (Aug 9, 2004)

plien69 said:


> I never said it evens out for you. I fully acknowledge that people who purchase premium are getting the short end. If that's a big enough deal for you, then buy a car that uses regular.
> 
> I did say that it evens out for the gas stations. Let's suppose all pumps are ultra accurate, and everyone gets exactly what they pay for. One person buys regular, one person buys premium. Then they swap 3/10 of a gallon after the fact. Isn't that what's happening now? The gas station doesn't make any more money. They still get $$$ for x gallons of regular + y gallons of premium, regardless of who pays for what fraction.
> 
> ...


Good points.


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## 7KRM (Mar 31, 2006)

plien69 said:


> Then buy a car that uses regular unleaded and take advantage of the situation. Fill your tank right after someone pumped premium, and you'll be getting 3/10 of a gallon of premium at the price of regular.
> 
> It's a zero sum game for the gas station. They neither make nor lose money on this "intentional deception." Yes, someone pays more than they should, but by the same token someone else pays less.


At face value it seems that would be true. However, a car designed to run on regular will not benefit from using premium. So, it's not like someone is getting something for nothing.

Yes, it may balance out for the station owner, but that's not the point on a consumer level. The point is the customer is not getting what he/she is paying for.
Saying one pays more while the other pays less and it balances out is a different argument. You want, and expect, to get what you paid for. 
Remember, when you buy gas the price is not negotiable.
Since the guy who only needs regular is getting some of your premium doesn't mean he's paying less, cause he can't benefit from the premium higher octane fuel anyway.

Back to the point, it's LAW that you get what you pay for. Thus, it's not just bitching for nothing. If you pay for 1 or 2 or 50 gallons of fuel, then you should get that 1 or 2 or 50 gallons. If the gas station does not give you what they charged you for then they are violating the law. It's that simple.
Just because people cheat all the time and get away with it, and we may know it's common or "the way things are", doesn't mean we should simply bend over, smile and take it. Although, for the most part we do.

That young girl did a very smart thing and should be applauded. This issue has been discussed in the past and it's a valid subject that cost's US citizens an unknown, though assumably, large amount of money.

The guy who said getting 1 or 2 gallons is not common, is missing a large number consumers. Those are people who have lawns and lawn mowers. Getting 1 or 2 gallon sales is very common and especially from spring to early fall.

T


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## plien69 (Apr 11, 2005)

7KRM said:


> Saying one pays more while the other pays less and it balances out is a different argument.


You're right. It is a different argument. I'm refuting the argument that gas stations are making a profit off the situation (3/10 gal regular vs. premium in your fill-up).

As for your other points, I see it boiling down to two main issues:
1. If a pump is dispensing less gas than it indicates, it is against the law and action should be taken. I agree with this. There is pump certification for a reason.
2. If you pay for x gallons of premium, you should get x gallons of premium, not x-3/10 gallons. For this point, I'll simply refer to my previously stated opinion that there is a limit to how fair we can make things. Getting 3/10 gal of regular when I'm buying premium is something I'm willing to accept as the consequence of the current state of pump technology.


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## kc5 (Aug 9, 2004)

7KRM said:


> At face value it seems that would be true. However, a car designed to run on regular will not benefit from using premium. So, it's not like someone is getting something for nothing.
> 
> Yes, it may balance out for the station owner, but that's not the point on a consumer level. The point is the customer is not getting what he/she is paying for.
> Saying one pays more while the other pays less and it balances out is a different argument. You want, and expect, to get what you paid for.
> ...


Amen, brother. You got it right. :thumbup: :clap:


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## kc5 (Aug 9, 2004)

plien69 said:


> 2. If you pay for x gallons of premium, you should get x gallons of premium, not x-3/10 gallons. For this point, I'll simply refer to my previously stated opinion that there is a limit to how fair we can make things. Getting 3/10 gal of regular when I'm buying premium is something I'm willing to accept as the consequence of the current state of pump technology.


I've always had a problem accepting mediocrity (that's why I drive a BMW). It often leads me to trouble. It would probably benefit me to lower my standards, but I won't. Is there a shrink in the audience......?


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## be-em-veh-808 (Apr 29, 2005)

I would question the 12 year old's testing method and technique. Perhaps not being very scientific.

For example. When I pump gas, each time after I finish and shut the pump, I alwasy lift the hose to make sure I get as much "left over" in the hose as I can get into the car. Well, for the next person that uses that pump (e.g. the 12 year old doing the experiment), if he/she does not do the same (lift the hose), then of course there's going to be less than 1 gallon. Get my point?


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## plien69 (Apr 11, 2005)

kc5 said:


> I've always had a problem accepting mediocrity (that's why I drive a BMW). It often leads me to trouble. It would probably benefit me to lower my standards, but I won't. Is there a shrink in the audience......?


Then do you demand to pay less when buying a Whopper without pickles? If not, are you accepting mediocrity?

There are things that are worth fighting for, and things that are not worth my time fighting for and/or thinking about. A refund for pickles on Whoppers, and 3/10 gal regular vs. premium are not worth my time worrying about. If you want to, that's fine. The value of your time and mental energy may differ. YMMV.


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## indyzhp (Mar 29, 2004)

gofishy said:


> Not defending the station owners but 2 things:
> 
> 1. I believe the pumps are calibrated on how they deliever 3 to 5 gallons not just one. Delivery may be slow initially then speed up. Not much call for just 1 gal. Can'r remember where I heard that!!
> 
> ...


I agree with gofishy. I have actually calibrated fuel flow meters and it is more difficult to calibrate to 1 gal. I always used a calibrated 5 gallon tank. One other thing that can lead to inaccuracies, is how close the pump is to the meter. When a pump is operating, the fuel is speeding up and slowing down, so the further away you can get from those pulses, the more accurate the meter will be.

I always fill up, and funny this thread came up, because I am currently tracking the "meter error" between what the onboard BMW computer calculates as MPG and what I calculate by the gas station meter and my trip mileage. I'm finding errors on the order of 3%. Yes, I am assuming the gas stations are accurate, so the BMW is actually saying it is using less gas than it actually is. OR the gas stations are saying they are giving me 3% more gas than they are. Hmmm. In reality, the error is probably shared between the car computer and the pump meter.

Anybody know the tolerance allowed by government standards for fuel meter error at the pump??


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## P.Chas (Nov 25, 2005)

In the U.K. regular and premium grades are usually dispensed via. separate hoses.
Problem solved by high technology!:thumbup:


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## kc5 (Aug 9, 2004)

plien69 said:


> Then do you demand to pay less when buying a Whopper without pickles? If not, are you accepting mediocrity?
> 
> There are things that are worth fighting for, and things that are not worth my time fighting for and/or thinking about. A refund for pickles on Whoppers, and 3/10 gal regular vs. premium are not worth my time worrying about. If you want to, that's fine. The value of your time and mental energy may differ. YMMV.


Who's fighting? :dunno: Just discussing. :blah: I can't see comparing pickles on a burger to not getting all the correct gas that I paid for, but let's just say that you are right and move on. :grouphug:


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## chuck92103 (Oct 9, 2005)

I think you folks missed the point of this thread. I don't believe gas pumps are all that accurate and can live with +- 5% accuracy.

However, the student found some pumps that were 50% off. Regardless if you get 1 gallon, or 100 gallons, the pumps should be closer than that. I found the 10-20% inaccuracy overall to be very bad. Remember, she did find a few pumps that were spot on. So I know it is possible to have fairly accurate pumps regardless of the amount dispensed.

However, 10-20% off on average is what caused me concerned. I would have never mentioned it if she found on average the pumps were 5% off. 

One note. Not one pump of the 50+ stations surveyed gave more than one gallon.

One thing people do not seem to get. Some folks or stations do not use the lock to hold the pump in the on position. So you have to use the handle. If you stop and start the pump several times throughout the filling process this could be an issue as well. 

Are pumps more accurate if you have no interruptions in pumping until the tank is full? I have no idea.:dunno:


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## plien69 (Apr 11, 2005)

I'm not fighting in this thread. I'm just saying I wouldn't fight for my 3/10 gal. of premium. 

Just so we're clear, there were 2 points made in this thread: 
1. gas pumps aren't accurate in the amount of total gas they dispense versus what they display
2. gas pumps dispense 3/10 gal regular when pumping premium.

I agree point #1 is important, and should be addressed, whether the discrepancy is 1% or 50%.

I equate point #2 to pickles on a Whopper, cream and sugar in coffee, what have you.


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## pilotman (Feb 2, 2006)

i am sure there are some gas station owners out there who would commit fraud in this way.

however, there is something fundamentally wrong with your 'claimed' numbers.

if you were buying 25 gallons of gas, and the reading was really up to 20% short as you claim, that would be 5 gallons short. NFW.

I have been pumping gas my whole life as I am sure we all have, and I can tell you any idiot could eyeball the situation immediately if they were shorting 3, 4 or 5 gallons at a time. It just doesn't make sense. Such a shortage would be really really noticeable.

i usually calculate how much I put in versus how much is in the tank and I have never experienced more than a half a gallon difference.

sorry, calling bullsh!t on the 10-20% fig


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## kc5 (Aug 9, 2004)

plien69 said:


> Just so we're clear, there were 2 points made in this thread:
> 1. gas pumps aren't accurate in the amount of total gas they dispense versus what they display
> 2. gas pumps dispense 3/10 gal regular when pumping premium.


To reiterate, it was Road & Track magazine that told me about the 3/10s a few years ago. I have not confirmed that number elsewhere. Could be spinning our wheels here for nothing.


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## chuck92103 (Oct 9, 2005)

pilotman said:


> i am sure there are some gas station owners out there who would commit fraud in this way.
> 
> however, there is something fundamentally wrong with your 'claimed' numbers.
> 
> ...


The test was a one gallon sampling. If you do a little research you will discover clever ways stations fool you. :thumbup:

For example, the first few gallons can be only 1/2 gallons, and then the rest is accurate. So in a 20 gallon tank, when filling up you would never noticed you are missing a gallon.

They can vary at which point the pump dispenses less thereby bypassing any standardized testing.

You ever notice at times on the gas pump meter the display that shows the gallons pumped speeds up and slows down? :dunno:


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## FenPhen (Jan 13, 2004)

What I see here is another case of a concept being relatively simple to understand (liquid comes out of a pump, so you measure it, and you get what you pay for) but has several physical, mechanical, and monetary complexities involved, and that makes for easy speculation.

As others have pointed out, this isn't a new problem. There are government inspectors that do this as a job, and they use equipment in a truck that lets them measure various volumes with the proper temperature and pressure adjustments. I know it's the government we're talking about here, but I'm going to give their methodology more benefit of the doubt than an 8th grader with a gallon container.

Others have already pointed out the problems of measuring the start and end of a flow, so doing several different measures with varying volumes (preferably one over the 10-gallon mark as well) would have been more scientific, even though she's probably on a budget. Ideally, she should have used a fixed rig that mounts the pump at a particular height, pumped a throwaway gallon to clear the hose, and then conducted different volume tests without moving the hose.

Did the girl verify her gallon container is a true gallon? Many portable tanks are larger than a gallon, presumably to avoid overfill or expansion problems.

The girl measured volume. But how about mass? This would at least control for density variations when she made her measurements. For your car, the mass of the gasoline is what's important.



kc5 said:


> The odds are greater that I will unwittingly get some regular gas than it is that a regular grade user will get some premium gas.


So why don't you go to a station that _doesn't_ send different gas grades through one hose? Most Chevron stations in Northern California have individual hoses for each grade. :dunno: I prefer individual hoses too.

An account of what a pump inspector does/encounters:
http://www.wcpo.com/wcpo/localshows/dontwasteyourmoney/fa4abb1.html

Here are the standards Seattle inspectors follow:
http://www.ci.seattle.wa.us/consumeraffairs/fsgspump.htm

A good read about how flow meters work and how gasoline is measured:
http://www.omega.com/techref/flowmetertutorial.html (don't draw conclusions from individual parts until you read all parts)


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## kc5 (Aug 9, 2004)

FenPhen said:


> So why don't you go to a station that _doesn't_ send different gas grades through one hose? Most Chevron stations in Northern California have individual hoses for each grade. :dunno: I prefer individual hoses too.


I do whenever possible. I use Chevron exclusively, but most here have switched to a single hose.


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## woody underwood (Feb 9, 2004)

I'm kinda slow on the uptake sometimes, so it took me a few days to realize that this thread is AN APRIL FOOLS JOKE! Pulled off pretty slickly though.


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## sdbrandon (Mar 18, 2006)

woody underwood said:


> I'm kinda slow on the uptake sometimes, so it took me a few days to realize that this thread is AN APRIL FOOLS JOKE! Pulled off pretty slickly though.


I doubt it. I lived in Colorado a couple years ago and a big news story broke about this very issue.

I think it is prudent to challenge services we use frequently to ensure we are getting a fair shake. i.e. Gas, Electricity, water, etc.

There has been a ton of articles written over the years uncovering corruption in each of these areas. Don't put your head in the sand or things never get better.


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## phuksi (Nov 11, 2005)

chuck92103 said:


> This makes no sense to me. If a pump is off the first gallon, it will be off subsequent gallons. It will not auto correct.
> 
> Fuel pumps should be accurate for each and every gallon. Otherwise, motorcycle riders would be penalized.


Well... every device that is used in measuring has its optimal range where the accuracy is greater than outside the range. For example a flow meter is typically designed and calibrated for a certain type of liquid (viscocity) and also flow. Typically when the flow is steady accuracy is good. In the beginning the flow is not steady and may result in greater inaccuracy. When the pump starts, it takes some time for it to get the proper pressure generated and when the flow is outside the optimal range accuracy is not the best. Also if the amount disposed is small like one gallon the leftover or the lack of it in the pipe after the gauge device throws the results all over. Now as you increase the sample size, the error that occurs in the beginning is relatively small when you fill up the tank.

That is all due to the nature of measuring devices and gauges. Sure we could create atomic accurate measuring devices but imagine the cost of gallon then...

I still agree that there is too much inaccuracy. And it makes you wonder... But I just wanted to write a comment that the devices used in pumps are not high tech but serves the purpose when maintained and calibrated properly.


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## rruiter (Feb 10, 2004)

kc5 said:


> I recall a 60 Minutes or 20/20 show a few years ago in which they discovered that many gas station owners were replacing their pump's computer circuit boards with ones that deliver less gas than the pump registers and what the customer pays for. The show uncovered a black market for these pump replacement parts. It's very simple for an unscrupulous station owner to do this.
> 
> On a related topic: A few years ago I had a letter published in Road & Track magazine (Tech Correspondence section) in which I mentioned that most gas pumps are now using a single delivery hose for all grades of gas. I asked that if the customer before me bought regular grade gas and I bought premium grade gas, is there any regular gas left over in the pump's line/hose so that I would be getting some regular gas in my purchase. Their answer was yes -- about 3/10s of a gallon of gas remains in the line/hose from its previous use. Unfortunately, Road & Track misunderstood the point of my question. They said that the 3/10s gallon of regular grade gas would not harm my car. My point, however, was that it's fraud if I get any amount of regular grade gas when I'm paying for premium grade gas. Just think about how much money the gas companies can make over time when customers pay extra for premium gas but are getting some cheaper regular gas. Any lawyers out there want to look into this? If so, please PM me so I can get my cut of your winnings. Could be class-action lawsuit.


I question your motive here. IF you get 3/10's of a gallon regular when first when you need it to be premium, the person AFER you who gets regular will get 3/10's of a gallon of premium first. The pump doesn't benefit from this at all ! no fraud.


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## kc5 (Aug 9, 2004)

rruiter said:


> I question your motive here. IF you get 3/10's of a gallon regular when first when you need it to be premium, the person AFER you who gets regular will get 3/10's of a gallon of premium first. The pump doesn't benefit from this at all ! no fraud.


No ulterior motives here. Jeez, how many times do I have to explain this? With all due respect..... lean forward and listen very closely, or as Michael Medved likes to say, focus like a laser beam. The issue is not that those precious few 3/10s of a gallon are going to waste or not being used by someone. Instead, the issue is that I'm not getting all the premium gas that I paid for. When I buy that first one gallon of premium gas at a pump with a single delivery hose, in reality I'm only getting 7/10s of a gallon of premium and 3/10s of regular if the guy before me pumped regular. If anyone thinks that's just fine and dandy, well good for them -- however, I don't. Period. That's it. Over and out. No mas. Nicht mehr. Pas Plus. Next.........

(I'm beginning to think that maybe Woody was right about this being an April Fools joke. I could use that beer now, Woody. :drink


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## rruiter (Feb 10, 2004)

kc5 said:


> No ulterior motives here. Jeez, how many times do I have to explain this? With all due respect..... lean forward and listen very closely, or as Michael Medved likes to say, focus like a laser beam. The issue is not that those precious few 3/10s of a gallon are going to waste or not being used by someone. Instead, the issue is that I'm not getting all the premium gas that I paid for. When I buy that first one gallon of premium gas at a pump with a single delivery hose, in reality I'm only getting 7/10s of a gallon of premium and 3/10s of regular if the guy before me pumped regular. If anyone thinks that's just fine and dandy, well good for them -- however, I don't. Period. That's it. Over and out. No mas. Nicht mehr. Pas Plus. Next.........
> 
> (I'm beginning to think that maybe Woody was right about this being an April Fools joke. I could use that beer now, Woody. :drink


Well, yeah, you are correct in that you (most likely) won't get that 3/10 as premium fuel. Will it make a difference on say 14 gallons wrt engine performance ? I doubt it.
If you want to be real sure your car gets premim only, Fill up after a bimmer just filled up, or find a station with seperate hoses. Or, fill a can of gas first for your lawmower motorcycle, chainsaw, what have you, then fill up the car. :thumbup:


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## woody underwood (Feb 9, 2004)

I started having my doubts when the coffee/cream/sugar and the Whopper without pickles thing surfaced...cold beer here and you're always welcome! Fun thread anyway.


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## kc5 (Aug 9, 2004)

woody underwood said:


> I started having my doubts when the coffee/cream/sugar and the Whopper without pickles thing surfaced...cold beer here and you're always welcome! Fun thread anyway.


Woody, I tried to send you a PM, but you have exceeded your storage limit and can't receive anymore until you delete some.


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## woody underwood (Feb 9, 2004)

kc5 said:


> Woody, I tried to send you a PM, but you have exceeded your storage limit and can't receive anymore until you delete some.


Just cleaned it out.......send away! 100 comes so fast when you have a ZHP.


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## LegoGT (Aug 3, 2005)

rruiter said:


> Well, yeah, you are correct in that you (most likely) won't get that 3/10 as premium fuel. Will it make a difference on say 14 gallons wrt engine performance ? I doubt it.
> If you want to be real sure your car gets premim only, Fill up after a bimmer just filled up, or find a station with seperate hoses. Or, fill a can of gas first for your lawmower motorcycle, chainsaw, what have you, then fill up the car. :thumbup:


After Katrina hit the gas prices went up to around $6/gallon around here. Thankfully I filled up before it all hit the fan, but I needed to refuel a few time in the middle of it all. I recognize that on the whole that extra 3/10 of a gallon doesn't matter, but since the prices were fluctuating so wildly I made an exception to my personal standards...

... I would pull up to each pump and look at the total sale price vs. gallons pumped. Then I'd do some quick mental math to see if the last person used Premium or not. I would only refuel at the Premium pump. Did/does anyone else do this?

... and after writing this I think I've answered my own OCD suspicions.


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## FenPhen (Jan 13, 2004)

LegoGT said:


> I would pull up to each pump and look at the total sale price vs. gallons pumped. Then I'd do some quick mental math to see if the last person used Premium or not. I would only refuel at the Premium pump. Did/does anyone else do this?


That doesn't even make sense.  The pump measures how much fuel of a particular grade has been pumped into the hose. Unless the meter has been tampered with, it will show the correct amount of fuel that has passed the flow meter, regardless of what mix of fuel you got out of the nozzle.


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## chuck92103 (Oct 9, 2005)

FenPhen said:


> That doesn't even make sense.  The pump measures how much fuel of a particular grade has been pumped into the hose. Unless the meter has been tampered with, it will show the correct amount of fuel that has passed the flow meter, regardless of what mix of fuel you got out of the nozzle.


:rofl: Yeah I know, but it makes for a good laugh anyway. :rofl:


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## MaxTimeOff (Jan 10, 2004)

Regarding flow meter accuracy and topping off.

Assuming that a pump was calibrated accurately, if you pumped continuously for 10 gallons at an even flow rate you would be more likely to get an accurate fill of 10 gallons as apposed to a situation where you stopped and started the flow several times during the same "indicated" fill of 10 gallons (in this example). In the stop start scenario you would conceivably get something less than 10 gallons, at least that's what some have claimed.

A recent "consumer advocate" news piece stated that topping off was not a smart thing to do for this very reason. Made complete sense to me, I now no longer top off. When the pump shuts off automatically I'm done with my fill.

Thoughts??

Also, LegoGT's comment that he looks for a pump that has previously pumped premium gas is an accurate methodology, completely anal, but accurate. So FenPhen and Chuck 92103 your comments that this makes no sense, make no sense to me.

If I pulled up to a pump and the previous sale was indicated at $35.00 with a volume of gas pumped indicating 10 gallons that would derive a $3.50 per gallon price of gas for the last activity on that pump. If premium sold for $3.50 and regular sold for $3.20 at this station, I could discern that this pump has premium left in the hose and I would get a full tank of premium, not premium - 3/10ths of some lesser grade.

How does this not make sense?


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## FenPhen (Jan 13, 2004)

MaxTimeOff said:


> A recent "consumer advocate" news piece stated that topping off was not a smart thing to do for this very reason. Made complete sense to me, I now no longer top off. When the pump shuts off automatically I'm done with my fill.


The accuracy of the flow meter is not the reason why you shouldn't top off. Besides the safety reason, the reason you shouldn't top off is because of the way the auto-shut-off mechanism works. There's a second pipe in the nozzle that triggers a valve to shut when the gas level reaches the mouth of that pipe (that's what causes the nozzle to click off). In a pump with a vapor recovery system, that pipe is used to suck back gas vapor and when the gas reaches that pipe, it will suck in that gas, so what you're paying for actually gets pulled into the pump's vapor recovery system (and you can damage that or cause the pump to malfunction for the next person cause it's plugged with gasoline).

Topping off wastes your money and can screw things up for everyone else. 



> If I pulled up to a pump and the previous sale was indicated at $35.00 with a volume of gas pumped indicating 10 gallons that would derive a $3.50 per gallon price of gas for the last activity on that pump.


Ah, he's looking at the previous purchase before he starts pumping, I see. Yeah, that's crazy. :loco:


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## LegoGT (Aug 3, 2005)

FenPhen said:


> Ah, he's looking at the previous purchase before he starts pumping, I see. Yeah, that's crazy. :loco:


I whole-heartedly agree that it's over the top OCD. I only did it when gas supply was unstable and you never knew if you had just found the last gas station still selling. So, when I saw a gas station that still had gas, _even if I only needed a few gallons_, I would stop and fill up... it might be another 10 gas stations until I found another not shut down. I used to drive quite a bit and would fill up almost every other day.

With (from what I thought was correct) 1/2 a gallon in the hose and filling up 5 times with 3 gallons each time I would then have 15 gallons with 17% being regular fuel (12.5 Premium and 2.5 Regular)... and that's where it seemed to make a difference -- not in price, but in the fuel my car was then using.

The point is, a lot of people in this thread were making a big deal about falsely receiving 3/10 gallon of regular when paying for premium. I merely wanted to let those people know that there's a way to ensure that the 3/10 from the previous driver was premium, as well. No more reason to complain.

Again, I apologize... it's the Engineer in me... I can't help it!


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## Pinecone (Apr 3, 2002)

1) Simple answer, DON'T FILL UP AT STATIONS WITH A SINGLE HOSE. If it bothers you THAT much, simply pick stations with individual hoses.

2) Due to the hose/piping from the meter to the nozzle, I woul dsuspect that there would be a good bit of measurement error based on how the person before hte studnet used the system. Pump until it cliks off then nothing, or turn off the pump and then squeeze the nozzle to drain the hose? Based on the second discussion in this thread, I would expect the possibility of some 1/3 gallon error form that alone. To be totally accurte one would need to pump some fuel (about a gallon) then shut off the pump in a consistant manner, then re-start and pump exactly 1 gallon. That would minimize that error.


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## Patrick330i (Sep 30, 2002)

Chuck, thanks for posting the results of the project from the fair. It's definitely food for thought. Next time I need gas for my mower, I'll take the 1 gallon container to my most frequently used service station and perform the little test. Should be interesting. I trust these dudes, let's hope I don't get disappointed. :thumbup:


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## crtroom warrior (Feb 19, 2009)

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## FalconGuy (Sep 27, 2002)

Jebus Christ, the lawyers are here to save us:thumbdwn:

Why dont you just buy your own ambulance and cut out the middleman?

If this gets any positive replies it will be a sign of the apocalypse


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## SC4ME (Nov 20, 2007)

FalconGuy said:


> Jebus Christ, the lawyers are here to save us:thumbdwn:
> 
> Why dont you just buy your own ambulance and cut out the middleman?
> 
> If this gets any positive replies it will be a sign of the apocalypse


It's worse than that. This lawyer had to resurrect a post from almost three years ago to troll for that lawsuit. :rofl:


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## passing through (Sep 10, 2013)

Reading this thread, I have to say BMW owners come across as a bunch of douches. Half of you are completely innumerate, and many of the others seem almost proud of not caring about the value you're not getting. Since most of this thread was before the financial crash and the great recession, I wonder if the board is still so blase' about saving money. 

The regulatory problem is that Weights and Measures blows off their responsibilities so that gas retailers can save a few pennies by only providing one hose per pump. That kind of cozy, look-the-other-way regulation tends to do more and more favors for bigger companies over time to the detriment of smaller competitors and consumers. It may all come out even over time, or it may not, sloppy measures are rarely in the consumer's favor. We don't take the time to think about $.10 a fill-up, but a station owner would be a fool not to think about a $200 a day opportunity. 

About the hose volume issue, by stopping a half gallon short of full (but how?) you would have room to pump 3/10 gallon of Regular to get all the Premium you paid for. But it would be more interesting to experiment and see how much fuel you get from a given pump if you use the "first handle click" flow rate, the "second click" rate, etc. I assume clicking on and off would give you the same or less gas -- if it gave you more, people would have figured that out and taken advantage. 

I have noticed that when I prepay for, say, $20 on some pumps the meter will get to $19.75 and then crawl for almost 30 seconds to get to $20.00. How many impatient young people will just leave their money for the sake of time? Hard to say, but if the pump is slowed deliberately to cause some to leave that would be ... a scam. 

I've also noticed that some pumps hit $20.00 and turn off the pump motor, but the handle's "squeeze valve" doesn't shut off for at least 10 seconds more. I assume gas I paid for is trickling out during that additional 10 seconds, but who knows? I usually shut off the pump by holding up the shut off flap where the nozzle goes back in the pump, but let any gas trickle out until the handle clicks off as well. If most people don't know they have to wait 10 extra seconds to get what they paid for, that would be ... a scam.

Finally, the accuracy of adjusting for temperature seems very sketchy. What if a cold front has just come in and the underground tank is 70 degrees while the above-ground pump is 40 degrees? Am getting a volume estimated based on the pump temp, the ground temp or the gas temp that goes from cold (dense) to warm (less dense)? 

By the way, the substitution of ethanol with almost a third less energy per volume for gasoline is the ultimate ripoff. Going above 10% ethanol as proposed will sell a lot of new cars by destroying older engines, but it will still be ... a scam.

It's easy to mock the idea of getting what you paid for or to suggest that it would be ridiculously expensive to have a better measure. But with today's technology it'd be very doable to get a truly accurate measure of what you're getting.


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## mb67 (Aug 12, 2013)

passing through said:


> TL;DR


:thumbup: Way to resurrect a *four year old thread!*


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