Grand Prix petro and octane

Just wondering if anyone would possibly know what might happen if someone was to put Premium in a Unleaded engine? I run about 89 octane (Mid-grade) in my stock 03 GT, but if I were to put 93 octane in it; what would it do? Any and all response is appreciated.

Nothing really. If you had some engine knock, it may help it then. If not, then you don't need the extra octane because your car is not really set up to use it to it's full potential...

87 or 89 is fine for a gt. 93 may last a little longer on the highway trips but the extra cost probably isn't worth it. It is a good idea if you will be far and away between gas stations for some reason.

You'll run fine on 87, like others have already said.

I have been putting 89 in for about a month now, and I believe there is a noticable difference in the performance/acceleration as opposed to using 87. So I was wondering if putting 93 in would make even more of a difference. Is it a bad thing to be using 89 on this car (2003 GT) already? It only has 5K on it, but I swear it gives it a boost. It's just that I have heard that you usually don't want to put in a higher than recommended octane until the car is older, and may need it to eliminate knocking...

You might notice a small power increase. I have heard that it may posibly hurt it. One time i put a little over 1/8 of a tank of Sonoco Race Fuel (CAM2) in and noting happen performance wise. I notice a small increase (not much) but I did get a nice rich race smell out the tail pipes.:D I had alot of people come up to me asking what my engine mods were, i lied a bit and they believed me:). If you do this, you must have the CAT removed from you exhaust. If not it will clog up quick.

I guess thats like adding 103 Octane boost. It says it adds 7 octane pts. So most people think if they fill up with 93octane and add 103 they would be at 100octane. But if you read the small print its .7 of an octane so your really at 93.7 octane. Paying $10 for less than a point.

Gasoline has 2 main parts, Heptane, ane Octane. 93 Octane gas has 93% Octane, with 7% heptane. 103 Octane boost(I think that it is supposed to be 104 Octane boost, but thats being picky;) ) I assume is pure octane, so that means that by dumping it in, you are increasing the percentage of octane in the fuel.

Higher octane gas for you right now will do nothing except burn cleaner.

Now if you went and got your computer tweaked - there are several places that offer this service like www.pcmforless.com - then you would be required to run a minimum 92 octane and would actually be able to notice a significant increase in performance. In a nutshell, octane is what makes gas stable - prevents it from detonating before its supposed to (this is what causes engine knock: when the fuel mixture explodes before the piston has reached the end of its compression cycle - or top of the piston chamber). In really high compression cars (like 13:1) or high boost turbo/supercharged cars, detonatoin can seriously fuck a motor. This is why the GTP's required 92 octane gas - take a normally aspirated 3800 with (I really don' t know) say 10:1(?) compression and force feed it to 3 or 5 (?) PSI and your compression will now be higher. A higher octane rating will be required not only stabilize the gas but also to get the most performance out the richer fuel mixture.

What happens when you get your PCM tweaked is that your timing/fuel & spark curves get advanced, and therefore you would need to run more stable gas in order to avoid detonation as well as reap the performance benefits of a higher air/fuel mixture.

I would personally go out and get this done to your GT's computer after you add headers, exhaust, intake, etc... However, these guys at PCMforless will customize your computer for a stock GT as well - you won't be getting as sick of a map, but you can always send it back to them once you modify your engine more to get an even more advanced program.

all I have to say is be careful with the really hight octane, 105 at the track is cool in a GTP but I got the bright idea of putting 110 in it one time and blew out my RT cat. Funny thing is I still passed emissions.

it burned your CAT out? i was told it wouldn't and it would plug it up.

When gas companies blend fuel to gain octane rating you have to give something up which is fuel mileage! Now GM designs the PCM with a certain octane rating to get the best performance and economy their is no way that nothing would happen something will change! You could get hard start problems in temp extremes but it would cause not permanent problems.

no using that fuel don't cause a problem. thats why i put it in my car for the hell of it. give the people driving behind me a nice smell of race fuel. :D

No doubt. The 89 has been great for me, and it hasn't caused any problems that I can see!!!! Going back to 87; now that would make problems:biggrin2:

LOL, yeah :bigthumb:

Originally posted by Scott 02
no using that fuel don't cause a problem. thats why i put it in my car for the hell of it. give the people driving behind me a nice smell of race fuel. :D

If you want race fuel go up to your local airport and buy some 100 low lead gas which is really 130 octane gas. Run that thru your engine!

oh, how much is it a gallon?

Does this mean that you're also planning on a turbine under your hood?

As I understand it, the GTs are tuned for about 89 octane and the GTPs for about 91. Without modifying/replacing the PCM there should be no noticable difference at higher octanes. Lower octanes, as we all know, have you using the right stuff next time.