I finally got my fiero running but it runs like **** since i haven't fully figured out the ignition timing but im not worried about that.

I hear gas from around the 80s was a higher grade than gas is today and I dont want the car to knock. so im wondering if I should use 87 octane or 93.

Lowest octane available is fine to use. Higher octane is usually used on high compression or turbo engines. The rule of thumb (unless it's specified by the manufacturer) is to use the lowest octane that doesn't cause pre-detonation (knocking).... which you will hear if it is happening.

[This message has been edited by Neils88 (edited 12-11-2023).]

quote BruhMans06: I finally got my fiero running but it runs like **** since i haven't fully figured out the ignition timing but im not worried about that.

For me, Ignition Timing is First than worrying about a grade of gasoline!

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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

87 in the US.
91 in some others.
Same gas but use different math to label octane on the station pump.

Yes, fix timing or other ignition problems fast. That will cause big problem(s) even use max octane available.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Yeah im not planning on running the engine much until I deal with the ignition timing, as well as the extremely worryingly loud screeching that emits from the engine. that's another issue I wish to know about, the engine screeches inconsistently when it idles, usually when you step on the gas and its worrying me quite a bit. Im hoping its the serpentine belt since I was having trouble tightening the alternator down. Also the thermostat housing continues to leak profusely, and since I cant find the right gasket for it (its the second iteration of the housing) imma see if I can just pack it with gasket maker and hope it works.

quote Originally posted by BruhMans06: I finally got my fiero running but it runs like **** since i haven't fully figured out the ignition timing but im not worried about that.

Make sure to have the ALDL jumper in place when using a timing light.

quote Originally posted by BruhMans06: ...the extremely worryingly loud screeching that emits from the engine. that's another issue I wish to know about, the engine screeches inconsistently when it idles, usually when you step on the gas and its worrying me quite a bit. Im hoping its the serpentine belt since I was having trouble tightening the alternator down.

The best money you'll ever spend on a 2.8 Fiero... Here.

[This message has been edited by Patrick (edited 12-12-2023).]

Ditto that Patrick! reb

I drove my 88GT 5 speed for several years for a job where I was doing 140+ miles a day on average. I regularly checked my gas mileage, and did that with 87 and 89 octane. My car ran better and got better gas mileage (more than the price per gallon difference, even in California) with 89. Don't be afraid to experiment with what your car likes the best.