Boxin' Robin wrote: ..."older" cars may benefit from using gas with higher octane levels.

If an engine (more specifically the combustion chambers) is badly carboned up, an increase in compression may occur, and therefore in that situation a higher level of octane (than originally called for) may benefit the engine. Otherwise you're throwing your money away.

If I may add my .02 cents. 

A stock V6 with stock ECM and clean combustion chambers, should run 87 Oct period.  My 88GT runs on a steady diet of 87oct from Shell, Chevron, or the Co-Op.  If you run Methanol Blended fuels IE Mohawk or Husky even their lowest grade 90oct, you NEED to advance your timing at least 2 degrees.  Ethanol blended fuels were never meant for Fiero's. My 88GT in its current setup runs like crap on Mohawk gas.

Now to the flip side.

If your car is running modified timing, either by computer mod or by simply cranking your timing up to 14 degrees you can/should run a higher Oct fuel. 

Now to Brian, he NEEDS to run at least 92 Oct in his car.  Why...  Because he has a modified 3.2 L stroker engine in his car with higher than stock compression, his base timing is set to around 14 degrees, plus his ECM has extra advance in the timing below 3000rpms.  This is due to a custom prom chip installed because of the cam and his 19# injectors.  

To wrap this up.   If your car is totally stock, run 87oct from a non ethanol blended gas station and you will be fine.       If your car is modified then run a higher grade gas.   There are about a million different configurations that could mean you need 89 from XX gas station or so on.  However I don't have the time or energy to go into all that.  

Just a side note, the gas that comes out of the pumps today is drastically different than what was around 25 years ago, when the Fiero and its ECM/Engine was being designed.  Our cars were never intended to run on Ethanol blended fuels, so you have to tune and setup your cars slightly different if you use Mohawk or Husky fuels on a regular basis. 

Capt David:

But aren't all grades of Shell fuel have Ethanol blended in them? The Bronze (87 octane) is what I usually put in all my cars. I think it says right on the pump that there is a minimum of 10% ethanol in the fuel.

Thanks again. Can't believe how much I've learned about car maintainance and cars in general after I got this Fiero a short two months ago!

I guess I should restate that.   I don't know what Mohawk and Husky do differently however the blend they use causes issues with a stock configuration Fiero. If you tune for it, you can run it, but totally stock you do loose power and drivability.  I think most gas stations have "some" ethanol in them, Chevron to my knowledge does not have any.  

        In my 4.9 I only use Mohawk and Husky as it likes the higher octane.   It almost boils down to Trial and Error with some cars.  If you have carbon deposits which lead to higher compression ratio's then the Ethanol blended fuels will be fine to use.  LOL, Maybe we should do a compression test day.  Check everyones cranking compression on their 1-3-5 cylinders of a V6 and all of the cylinders on a 4.  Anyone with less than 150psi should run 87, 180psi 89 and 200psi 91-94.    

For the record my old 2.9 built up V6 was around 220psi and loved 94oct.  However my 88 V6 has 130psi and I run 87oct.  Both engines got 26-32mpg gas mileage on highway drives.

Capt Fiero wrote: Maybe we should do a compression test day.  Check everyones cranking compression on their 1-3-5 cylinders of a V6...

Me thinks you're being discriminatory against cylinders 2-4-6.

Patrick wrote: Capt Fiero wrote: Maybe we should do a compression test day.  Check everyones cranking compression on their 1-3-5 cylinders of a V6... Me thinks you're being discriminatory against cylinders 2-4-6.

LOL, I only said 1-3-5 as they are the trunk side, if you want to do the 2-4-6 on the firewall side, you are more than free to do so.  LOL.

Pfft, compression is for sissies.

(I only say this as I'm sure poor Gretchin has some tired lungs by now... Hello 7.0:1)