OMG! Have I been using the wrong fuel?? - BMW Forum

Kaligiy83 · 03-31-2006, 02:45 AM

So I've had my 1995 bmw (325is auto) for about four and a half months now. The first day I got the car, I filled the tank with 87 octane grade fuel (mistake! I know). I later discovered, after the car began to run slightly differently, that switching to a higher grade of fuel might help its performance. Since then I've been using 89 octane grade fuel and it seems to have helped until just recently, however, when i noticed that my car seems to be losing power, epsecially when its idling (on a cold day). Even rolling the windows up seems to disrupt the otherwise steady idle.(rpms jump then level) SO my question is: Am I supposed to be using an even higher grade of fuel? Like 91 octane? Is the 89 octane fuel that I have been using for the past four months to blame for rough idling and power loss? Thanks for the tips in advance. Crap! I hope I havent done any serious damage

used:

vwk · 03-31-2006, 04:06 AM

I think you should be looking at the alternator or your battery...

SpooldUp · 03-31-2006, 07:53 AM

Yeah when I run all windows up at once or run the top the initial surge makes the revs dip. No biggie - just the alternator working putting a load on the engine. Now if your car nearly stalls out, you have a problem.

RexKing86 · 03-31-2006, 09:26 AM

for the E36 (in most cases) i believe there are 2 alternators. Mine had been replaced, but by the 80amp, not 140amp before I puchased it. Im sure you have the 80amp like me. To make up for the less powerful alternator, the computer has the car rev up to get more electrical power when needed. It has nothing to do with your fuel. Im sure its fine, but if you do get a new alt, get the bosch 140amp.

PS- I would still also always use 91!

BavarianHotCake · 03-31-2006, 09:58 AM

I used 89 for the longest time because of gas being so expensive. I was stupid. Alwayse use 91. I could tell the difference when I changed. It is totally worth it.

drz · 03-31-2006, 10:31 AM

cliff notes: have your electrical/charging system checked and use 91 from now on

98three28i · 03-31-2006, 11:49 AM

unless you are big into car audio and your name is Alma Gates, you probably dont have two alternators.

drz · 03-31-2006, 01:26 PM

Quote:

Originally Posted by 98three28i

unless you are big into car audio and your name is Alma Gates, you probably dont have two alternators.

He meantt that two different alternators are available in the market for e36s. The car runs on one alternator, which can be a 140 Amp or a 80 AMp unit. Well, at least that is how it is. I don't know if he is aware of that, but tha is what he should have meant.

tomctx · 03-31-2006, 03:50 PM

I've always run 89 octane, no problems whatsoever. the owner's manual says I can use higher octane for more performance and less mileage. I ran 93 octane for a couple of months. I could perceive no performance gains nor any mileage loss. Decided to save money and went back to 89. YMMV.

e36surge · 03-31-2006, 04:03 PM

every 4th fill-up I put 91. No more 93 in these parts. I see very little difference. I also use an injector cleaner every change of season.

Take a close look at your electrical system, alternator and battery... and while you're at it an electric supercharger should make them windows open and close real quick... (JOKE)