Hey all,

New to this forum! But so far it looks pretty awesome!

Recently purchased a 2004 Supercharged SS with 115,xxx miles and I'm loving it! But I'm kind of worried about the gas I have been putting in it... I honestly don't remember the level of octane :S I know it is the middle option out of three, but I don't know if the station I use (BP) has 87, 89, 91, or 93.

I know that my car is designed to run on 91 and higher. So my question is, what are the problems that may have already occurred for running lower-than-minimum octane in my car for the last 7,000 miles? And if I can't buy any higher than an 89 octane, how should I go about injecting more? I know I can buy some at any given store, but any suggestions?

Thanks everyone!

 

Lower octane gas than suggested can cause knock. This is usually only an issue when the engine is seeing boost. The PCM will pull timing when it detects knock (to a certain extent), but it's never a good idea to run lower octane gas than is recommended.

Most (if not all) of the octane boosters that you'll see at autozone and whatnot are crap. Your best bet is to top off the tank with as much 93/91 as you can, although if you really wanted to you could add a bunch of toluene or xylene to the gas in your tank (google homebrew octane booster to figure out proportions).

 

Thanks so much for the quick response!

A friend of mine (owns a 5.3L GP GXP) asked to make sure I was using high octane fuel and I knew I wasn't putting in the best, so I started getting a little worried. Then I saw it can cause pre-detonation and chipping of pistons. I'm definitely going to look into the options you gave though. Thanks again!

 

If you're really worried about damaging the motor with low octane, unplug the BBV solenoid - you'll only run ~4 psi of boost, but you won't have to worry about blowing the motor

I say just find some 93 octane somewhere and fill er up

 

i think his worries is that he has been running low octane for a while now.

i would deff go to 91+ from now on.

but to check what could have happened, i would recommend pulling the plugs and checking them. if they are whitish then the engine has been running lean. if they are dark then it has been rich. if your unsure, then take pictures and post them up.

i'd also recommend buying a scan tool like an aeroforce gauge to scan acutal boost and KR while your driving ... its a fun and protective tool that is a must!

 

Thanks guys... z34phoenix nailed it. I'm worried about what has happened in the couple thousand miles on 87 (it is 87, i checked). But when I checked I also found that the highest I can get is 90 which has some ethanol in it :S is it worth it or not? What should I do?

 

Likely nothing, assuming that you are using a stock s/c pulley/tune and assuming you weren't beating on the car for that 7k miles. The 3800 block is pretty resilient and like I mentioned before the PCM will pull timing when it detects knock, so I wouldn't really sweat that 7k miles on 87 too bad unless you are already seeing an issue.

90 octane seems like an odd number for an octane blend, but it would be worth using instead of 87. I wouldn't worry about it having ethanol in it at all (ethanol actually has a higher octane rating than petroleum gas). As z34phoenix said, it would be a good idea to have a way to scan the car for KR especially if you get a little heavy on the throttle from time to time.

 

Generally with a stock 3.8 pulley, you don't mess anything up with lower octane, just decreased performance. It couldn't hurt to get an Aeroforce guage like z34phoenix said though, that thing has saved my motor several times lol

 

Totally agree with the above- just start using premium from now on, and don't floor it again until you get it filled up with premium.

As far as potential damage- I wouldn't worry at all. Unless you had some odd combination of issues and problems. I've never seen proof of chipped pistons on a stock pulley. That's not to say it couldn't happen if your fuel pump was dieing and running stupid lean - and you were knocking on top of that or some other combo.

 

ethanol? its safe to run that?