# What Octane gas is best?



## 1997328is (Nov 26, 2003)

What octane gas is best in a 1997 328is? I bought the Beemer used and dont have a manual for it? and could using the wrong gas cause the check engine light to come on?:dunno: 
Thanks


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## brave1heart (Jan 7, 2002)

1997328is said:


> What octane gas is best in a 1997 328is? I bought the Beemer used and dont have a manual for it? and could using the wrong gas cause the check engine light to come on?:dunno:
> Thanks


Not sure about the E36 but I'd think it's the same as the E46. The minimum required for the E46 is 91, although I always put in 93. The difference in acceleration is noticeable. Even more noticeable is the difference in acceleration from 93 to 94, which I tend to use for autoX and track events.


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## The Other Tom (Sep 28, 2002)

1997328is said:


> What octane gas is best in a 1997 328is? I bought the Beemer used and dont have a manual for it? and could using the wrong gas cause the check engine light to come on?:dunno:
> Thanks


I'm pretty sure the 2.8L engine takes mid grade gas. Also, your car probably has a knock sensor that will detect engine knock and cause your car to "de-tune" (and eliminate the knock) if you use a lower grade. I don't think you'll get a check engine light because of this. You probably won't even notice it, except maybe a loss of power.


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## KC Ron Carter (Nov 19, 2003)

*hmm,*

octane is like after shave lotion, it can be overdone.

Only use what is needed. If you stink use it.

87 octane gasoline is the most thermally efficient.

More power for the gasoline used.

Higher octane is a slower burn pattern to prevent detonation.

Most vendors use alcohol to get higher octane and it is a slower and colder burn.

And the possibilty of higher octane providing more HP is a little hard to show or believe.

Later,


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## LDV330i (May 24, 2003)

1997328is said:


> What octane gas is best in a 1997 328is? I bought the Beemer used and dont have a manual for it? and could using the wrong gas cause the check engine light to come on?:dunno:
> Thanks


There is a decal inside the gas cap door with the minimum octane required.


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## SupraRZ (Apr 16, 2003)

100 octane 

C16


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## xfactor (Nov 5, 2003)

brave1heart said:


> Not sure about the E36 but I'd think it's the same as the E46. The minimum required for the E46 is 91, although I always put in 93. The difference in acceleration is noticeable. Even more noticeable is the difference in acceleration from 93 to 94, which I tend to use for autoX and track events.


I don't think I've ever seen 93 or 94 octane gas. In Arizona, the highest grade gasoline available is 91 octane. We lost 92 octane a couple of years ago.


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## 3Valkirie (Nov 21, 2003)

I have a `96 328is and a `97 528i, bot have decals on the gas cap that says use 89 (AKI) octane fuel. Both will run on 87 in a pinch (knock sensor will compensate for lower octane, at the price of performance), and will benefit slightly from higher octane (i.e. marginally better performance), but it doesn't make sense to pay for octane you don't really need, so I run mid-grade (89 octane) gas.

That being said, after the right octane, the next most important consideration is the detergent additives - some brands only offer it in their top grade of gas, e.g. Mobil, while Exxon, Shell, Texaco. Chevron, Amoco, have the full additive pakg in all grades of their product. The detergent helps keep carbon and other crap from building up on your valves (which will lead to 'octane creep'), and a bottle of Techron or BG44K is a good idea every three months or so. HTH :thumbup:


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## rwebbe (Jan 20, 2002)

*Citgo?*

Orange light lit, computer reading 43 miles to go ran into a Citgo 7/11 for 93 Octane. I usually have been using Shell, but any port in a storm especially when cell is out of juice. Question is, does Citgo have the cleaners like others you mention?


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## rwebbe (Jan 20, 2002)

Neglected to add on my last post for those interested, tank took 15.4 galloms at $162.9. About 1 gallon left to do whatever comes natural with such a fine car.


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## Nick325xiT 5spd (Dec 24, 2001)

Here's my standard "use premium" response:

http://www.dynospotracing.com/octane.htm


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## Jspeed (Dec 23, 2001)

Nick325xiT 5spd said:


> Here's my standard "use premium" response:
> 
> http://www.dynospotracing.com/octane.htm


That's good, but here's something more comprehensive. :angel:

http://www.caranddriver.com/article.asp?section_id=4&article_id=3604&page_number=1


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## xfactor (Nov 5, 2003)

rwebbe said:


> Neglected to add on my last post for those interested, tank took 15.4 galloms at $162.9. About 1 gallon left to do whatever comes natural with such a fine car.


Are you telling me you pay over $10/gallon for gas?


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## The Roadstergal (Sep 7, 2002)

Nick325xiT 5spd said:


> Here's my standard "use premium" response:
> 
> http://www.dynospotracing.com/octane.htm


But is that what happens with a 1997 328is on 89 octane? :dunno:

I wish there was some way to attach a readout to the knock sensor, so you could tell when it was kicking in and make intelligent decisions about what gas to use for your own car in your own environment.


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## Nick325xiT 5spd (Dec 24, 2001)

My '94 325i (which asked for regular) improved noticably when run on Premium. I'm going to make the ASSumption that if the M50TU and the M54 notice it, then the M52 probably does as well.


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## rwebbe (Jan 20, 2002)

Oh come on Xfactor. I paid one dollar and sixty two cents plus the 9 10ths on the end of that. My proof reader needs an over haul. Me too I suppose. My only point, keep the injectors squeeky clean. Luck.


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## 3Valkirie (Nov 21, 2003)

My cars run fine on 89, a little better on 91/92/93, mileage is the same on either. I believe that the folks at BMW know a thing or two about gas flow, cylinder head design, and electronic engine management and don't think that they'd set up an engine to ping or otherwise run poorly on lower octane fuel just in the name of 'fuel economy', not to mention potentioal engine damage and waranty problems/expense. My cars are going on 8 and 7 years old, respectively, and they run strong, thank you. If they rate the engine for 89 cotane, you can use 89 octane, no worries. Their middle name is "MOTOR", afterall.

While I have no doubt that higher octane will produce more HP/torgue in a given engine, I don't know that it makes a whole lot of difference in day-to-day driving. For driver's schools, solo, other track time, by all means use super juice, for commuting, give your wallet a break, but it's up to you. In the interest of full disclosure, would Nick325xiT 5spd be kind enough to post the specifics on the engine/car that was dyno'ed??

Re: Citgo. IIRC, they did have an addive pkg in all grades of their gas, but in my area, they were using alcohol as an oxygenate (for 'cleaner air'?). Oxygenates (such as alcohol, MBTE, etc) tend to foul valves faster, and it's either a good idea to avoid brands that use them (though this can be difficult in high pollution areas like Denver or Phoenix) or use Techron regularly.

For a definitive answer, I'd contact BMW/NA. They used to have a list of preferred brands of gas. (Plan B - see if your local CCA chapter has a library with back issues of the _Roundel_ or e-mail the tech guru at the magazine) I learned of this back in the mid-`80's, when they went away from the 'eta' engines, back to 'proper' BMW high compression/rev'ing/performance mills, when valve fouling was a big problem. HTH. M2


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## The Roadstergal (Sep 7, 2002)

3Valkirie said:


> While I have no doubt that higher octane will produce more HP/torgue in a given engine


I doubt. I don't think I'd get an iota more hp running 89, 91, or 100 in my eta.  For cars without knock sensors, it's easy - if the car pings, bump a grade. Cars with knock sensors make it all more difficult, which is why I wish there was some objective way to tell if it's kicked in.

Sure, a car may feel faster with higher octane, but feeling and going don't always go hand in hand. Unless you pop it on a dyno under similar conditions, you just can't tell.


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## 3Valkirie (Nov 21, 2003)

Point taken RG, I liked the eta engines for what they were - an efficient, low-pumping-loss engine with plenty good torque down low. More octane wouldn't really do anything for them, but good detergency in teh fuel is still important. I perhaps should have said something to the effect that engines with knock sensors may be able to take advantage of higher octane, but I don't know enough about DME to know if the stock controller will try to 'proof' the gas to see how aggressive the ignition timing can go without knocking. FWIW< the car's manual does allow as how there may be minor performance benefits with higher [than 89] octane.

I've spent a liitle time with the folks at Autothority and have had one of their chips in a previous car (`87 325is). Their software mods require 92 octane, not becasue any mechanical modifications, but because the software provides a fatter fuel flow curve and more aggressive ignition tuning allow the engine to take real advantage of the higher octane. The chip did provide a tangible increase in performance and improved throttle response at a very cost effective price. The improvement isn't as dramatic in more recent models, as I believe, BMW is doing a better job of exploiting the current architecture's capabilities, but the bump up in the revlimiter and removal of the governor still makes it a desirable mod.


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## Jspeed (Dec 23, 2001)

Can an OBDII reader retrieve the ignition timing data? That'd be an easy way of checking whether the computer is retarding the ignition to suppress knocking.


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