# DIY Oil Changes and DEF



## Fleetman (Jul 31, 2010)

I'm changing the oil in my 35d at about the mid-point of the BMW oil change interval....roughly 6k miles at this time.

I'm filling the active DEF tank at the same time.....what do the rest of you do? Just curious and I noticed, whilenthe active tank only took a pint or so, the reserve tank took the remainder of the liter bottle....not sure if it's full or not.

Thanks in advance for your replies!


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## Flyingman (Sep 13, 2009)

Fleetman,

Read some of the info posted on the oil change interval and oil analysis in My Latest Oil Report. I'm personally convinced you're throwing your money away doing premature oil changes. But if it makes you happy, go for it.

The DEF Tanks holds something like 6 1/2 gallons of DEF. So if all you put in was a liter, you have not filled it up with 6k miles on the car.

The DEF fluid is meter pumped to match with fuel consumption, at a rate of about 1-3%. You can do the math and estimate how much DEF you've consumed in 6,000 miles. I'd say you have consumed almost 1/2 your tank, so should need about 3 gallons of the stuff.

Let us know what you find out.


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## Fleetman (Jul 31, 2010)

yup...I understand what you're saying and I'll continue with what I'm doing....most of my driving is high speed for 90 minutes in the AM but the evenings are much throttle on-off-on-off, over and over again for close to an hour and then high speed again for the remainder of the trip. I would worry more about excessive soot and fuel contamination than anything else therefore I change my oil more often than recommended....not interested in doing oil analysis, changing strictly by my seat-of-the-pants method.

I do NOT agree with BMW's oil change interval....it may work and I'm sure it does but if it doesn't then it gets a whole lot more expensive than too-soon oil changes. And even then, the money doesn't matter as much to me as the time that would be consumed plus the additional expense of having to commute 150+ miles per day in one of our gas-guzzlers while I repair this one.

I think I'll lay in a little supply of DEF and fill the tank completely.

Thanks for the reply!


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## F32Fleet (Jul 14, 2010)

I used to do mid-OCI oil changes but have stopped due to the potential downside of increased wear rates (Too lengthly to address here but there is an SAE paper on it). DEF addressed as required per the CBS.

For some reason I think 10k mile OCI is ideal but will confirm via UOA now that I'm passed break-in.
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## floydarogers (Oct 11, 2010)

Fleetman said:


> I think I'll lay in a little supply of DEF and fill the tank completely.


There's another thread around that mentions where to buy (5 gallons) from auto parts/truck stops, and how to modify containers to be re-usable or as a funnel. Search will probably find it.


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## listerone (Jul 21, 2009)

Fleetman said:


> I think I'll lay in a little supply of DEF and fill the tank completely.


I'm on my second DEF equipped diesel.With my "d" I never had a low fluid warning thanks to the "free" annual maintenence.With my Bluetec I started getting "low fluid" warnings at about 19K miles (not bad,I'd say) and that was remedied by having the 2yr/20K service done at the dealer.Part of that service involved purging *and* refilling the tank which,I believe,is what BMW does as well.Purging,I've read,is necessary because of the possibility of crystals forming in the tank,something that must be avoided.Everything I've read about DEF clearly states that it has a finite shelf live after manufacture...and that finite life applies when it's in the vehicle's holding tanks as well as in a jug in your garage.Given that,my policy is not to stock up on...or add...fluid unless/until you get a warning.Of course once you get a warning it's probably wise not to ignore it particularly if you plan to travel in the middle of nowehere.


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## KeithS (Dec 30, 2001)

listerone said:


> I believe,is what BMW does as well.Purging,I've read,is necessary because of the possibility of crystals forming in the tank......,my policy is not to stock up on...or add...fluid unless/until you get a warning.


BMW no longer purges the DEF tanks, they just fill them. With some common sense should be able to stay out of trouble. One is not to keep topping the tanks off, let them get real low before you refill so the majority of the DEF will be fresh. Also as you already said, buy DEF when you need it so it's fresh, do not store DEF for a long time.

If you're on the road away from home and really need to go more then the 1000 miles once the warning comes on, you surely will be able to find a VW (or BMW) dealer (in the 1000 miles) to purchase the 1/2 gallon bottle, which will get you at least another 1000 miles.


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## Penguin (Aug 31, 2003)

KeithS said:


> If you're on the road away from home and really need to go more then the 1000 miles once the warning comes on, you surely will be able to find a VW (or BMW) dealer (in the 1000 miles) to purchase the 1/2 gallon bottle, which will get you at least another 1000 miles.


Truck stops also sell it, although it might be in containers which do not have the "mess-proof" filling attachment. I believe parts places, such as NAPA, also stock DEF in gallon-sized containers.


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## Fleetman (Jul 31, 2010)

I don't mind buying it in the BMW containers...I should have said I want to top it off this time and plan to run it fairly empty before filling it again. I am aware of the shelf life, especially once "unsealed"

I'm familiar with DEF but all of the tanks in our equipment are visible....not like these.

Anyway, thanks for the replies.


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## KeithS (Dec 30, 2001)

I will repeat the deal with the containers. There are 2 different kinds. There is the 1/2 gallon jug with the exact valve/fitting to fit the DEF ports. You can get it from BMW for about $25, or the EXACT SAME thing from VW for about $11. This is intended for a quick fill to extinquish the 1000 miles to no start condition, generally until your next free scheduled maintenance. 

Then there is the common 2.5 Gallon jugs. These are sold everywhere from truck stops, to auto parts stores and even BMW. But none of these, including the ones from BMW will have the fitting for the port. You can get it from BMW if you like paying more for them, but still the same thing as the parts stores. 

Now what many of us have done was to get the 1/2 bottle with the correct fitting, and reuse that bottle, or turn it into a funnel for transferring from the 2.5 gallon jugs. In fact that is exactly what my dealer does. They cut a hole in the side of the 1/2 bottle (will face up when screwed onto the 335D - guess you would cut the bottom off if using for X5), and pour the DEF from the 2.5 gallon jug into the 1/2 gallon bottle with the hole in it attached to the vehicle. For the 335D it is a 2 person operation, one to hold the 1/2g bottle attached to the car and to push it in to open the valve, the other to pour from the 2.5G container. They use to have this official BMW funky fitting with 2 hoses and decided using the bottle as a funnel was easier.


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## DC-IT (Sep 27, 2009)

Last month I had to fill up my DEF as the low def warning showed up but all I could managed to get into the tank was a 2.5 gal container. 
When I tried to get more in via the passive tank inlet it would take no more.

Has anyone successfully refill with the 5+ gals required?
Or is there a special technique to do the refill?

FYI I use the 1/2 gal bottle and refill it from the 2.5 gal bottle.


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