When I bought my car he said put prem (93) in it but mid grade (89) would work just as good. Can I use regular? Its a 5.7 Liter

 

any mods?

any heavy advanced timing?

My car with bolt ons and some timing would run on 87 regular just fine, but i always ran 89 octane or 91 depending where i was at.

 

no bolt ons. The real major mods is air filter and exhaust but I think im going to go with 89

 

After doing a little searching I've found this from the owners manual on a 96 vette.
But it also says you may use lower octane gasoline, but your vehicle's acceleration may be reduced.

It says that if you use gasoline with a lower than 87 octane rating, you may get a heavy knocking noise when driving. If you use gasoline with an octane rating lower than 87, it recommends that you use 87 or higher as soon as possible.

Owner's manual says 91 octane and above . It says the cars computer will adjust the timing to run on regular or mid-range to prevent knocking but not to make a habit of it .

 

thank you

 

i noticed no difference at the track between 87/89 mix and pure 93. these cars with iron heads and the compression we have, you can run anything. I just ran 89-91 since i advanced my timing alittle and wanted to keep detonation/knocking down to a minimum, but my car showed very little knock retard untill i started getting more aggressive with it

vettes have aluminum heads and higher compression so they may want to use 91 octane

 

You only need enough octane to resist detonation when under load. If the grade is too low and the computer retards the timing, the engine will still run but you'll have less power due to the retarded timing.

The only way to really know is to use a scan tool to see knock counts when the engine is under load. A higher grade of octane may seem like it makes more power but it's just the computer not changing the timing.