What does this mean?

Argeo · 10-27-2003, 06:03 AM

I read someplace that I may be wasting my money using 89 instead of 87 octane gas on my 77 3.0 911. Well, Saturday night I started my car and drove to the gas station. I kept the engine around 2,000 rpms the whole way since it was cool and had been sitting for a week. Well, I put in 87 and some injector cleaner and I notice after a little while, the car will not go above 4,500 rpms. Does that seem gas related?

Thanks in advance.

Superman · 10-27-2003, 08:04 AM

No. A couple of octane points will not change the amount of power you have. Your engine must have been running poorly even with 89 octane gas.

FWIW, I use Chevron Supreme exclusively. 91 RON. Just because I care. Probably don't need it. Then again, I probably don't need most of the stuff I buy.

Tim Walsh · Tim Walsh's Garage

I'm not sure about the specifics of your car but on mine I was told to use regular as the extremely low compression needed the lower octane to burn better. BUT that's with 7.5:1 compression.

MotoSook · 10-27-2003, 08:08 AM

You could have gotten some dirty gas! Or the cleaner worked some of the crud in your tank loose, and now you filter and injectors are dirty.

I spent days troubleshooting after a similar episode!

Change the fuel filter...mine was less than 3 yrs old.

Of course, check all the usual suspects, ginition, pressure, etc,..

Joe Bob · Joe Bob's Garage

Unless the service station uses a blend valve to mix 87 and 91.....most mid grade gas has sat quite awhile and rends to have junk in it. It's not a big seller. The trend nowadays is to see blended gas for mid grade or no mid grade at all.

If you find that your gas is indeed contaminated, I would suggest that you call the local enforcement authority. In California it is Weights and Measures. They deal with gas meters and adulterated fuel.

IROC · IROC's Garage

Using fuel with a higher octane rating than what the engine requires has got to be the greatest marketing ploy of all time. The thought is that the higher the octance number, the better the fuel must be! Heck, it costs more, it's got to be "better"! Wrong!!!

Octane is nothing more than a rating that determines a fuel's resistance to pre-ignition. The higher the number, the higher the resistance. If your engine doesn't pre-ignite on 87 octane fuel, then anything higher is just a waste of money. Period. (barring newer engine technology that actually maximizes ignition timing based on knock sensors - but that's not what we're talking about here).

Mike

MotoSook · 10-27-2003, 08:15 AM

And...if bad gas is the case, drain you tank! Get that crap out of there.

Argeo · 10-27-2003, 08:36 AM

Thanks for the replies guys. After it happened, I put the car in the garage. Well after talking to my neighbor about the whole thing, he recommended I bump up to 93 and see what happens. well of course, when I went to get the 93 my neighbor came along and everything went as normal for the short 3 min drive to the gas station. I put 93 in there anyway and let him drive and it went fine. He thinks that my car may have a higher compression ratio than 8.5:1 due to some past history I have been able to accumulate and because of it's pep. Anyways I think for the extra $.15 and the frequency that I drive, maybe I will just stick with the 89. Maybe something did gunk up an injector momentarily. I will take out again when the weather gets dry and keep you posted.

Thanks as always.

Argeo · 10-27-2003, 08:41 AM

Oh, and the car was running great before this happened. The only problem I do have is that until the car warms up, it will not fall back to idle properly but just die. When warm, not a problem. No backfiring, but the rpm's would sometimes bounce until either it settled or it just died. I am still working out that bug. Any suggestions?

stlrj · 10-27-2003, 10:35 AM

Yeah, go back to regular and avoid adding too many variables to the situation or you'll never figure it out.

Joe