just curious what is better for my 305 tpi v8 engine?

87 89 91 or 93 octane?

 

WOW your not even a newbie, and yet you asked this question, there are a bunch of threads about this, . Plus your the only one that can decide what is best, Your budget, your driving style. Plus engine mods.

 

not a newbie but the car has barely been driven since my restoration started.

so i dont know what it likes and what is a waste of money

 

well lets just say back in 2002 i was running ultra 94(thats right) 94 but sunoco discontinued that,, so i ran 93 up until last year when i ran 89. now today with these prices i run mainly 87,, if i get a good tip at work ill fill her up with 89 BUT NEVER FELT A DIFFERENCE EITHER WAY its all crap unless your seriously built up

 

Im usually good with 89. If I put in 87 my mpg goes down and engine sometimes pings. If you look in the owners manual it says to put in premium(thats 91 here in CA) so I try to whenever I can.

 

What's your compression ratio? If its a stock engine then its 9.3:1 and you can run 87 in it if you dont go racing. However, an engine with high mileage will have deposits on it that will require more octane to stop knocking and pinging, so its a matter of trial and error. Run the lowest octane that stops the engine from pinging. If it doesnt ping on 87, then run that. If it doesnt ping on 89, then run that.

 

Well, I always put in 89 no matter what. Kinda the happy medium. And I've been able to tell a difference. I don't get any backfire, exhaust smells nice and clean (for exhaust lol) and generally makes it run cleaner, to what I've found at least. Anytime I ran 87, it just ran like crap :/

 

The two most important factors will be ambient temp, and compression ratio. The higher octane the gas, the more resistant to detonation it will be, at any given temp. You should be able to run 87 in the winter, and maybe even the summer, depending on how hot it is outside. The higher the outside temp, the more prone the engine will be to pinging/detonation. There are other things that could make a difference too, such as forced induction, nitrous, etc, but that's the short answer. With that said, start with the lowest octane gas, see how it runs, and go from there. It's also worth mentioning that pretty much all gas is the same, even from different stations. It all comes in the same pipelines from the refineries, the only difference between brands is the additives (Techron, etc).