What'* the minimum octane requirement stated in your owner'* manual for the L67? The reason why I ask is because out here in CA, there is no 93.

Edit: I think I remember willwren telling me that you guys can run the 91 unless you've swapped supercharger pulleys; am I right?

The L67 minimum rating depends on the year.

Many of the manuals say "Premium ONLY", however I remember my 95 manual saying "You can use other grades, just don't expect power or gas mileage". The 95 book was really saying: Hope the knock sensors work and never go bad.

Using the highest rating you can buy is the L67 way.

I use 93, mostly because I want the highest, but also because 91 is hard or impossible to get. I've seen 92 a couple times. In most cases 91 is the minimum octane needed.

There are no hard and fast rules..."do X if you have Y". Even the owners manual is just a guideline. And yeah, that sounds about right..the SC engines are running higher compression ratios over N/A motors, so they are more likely to run into engine knock on lower octane gas.

You run the gas with enough octane to prevent pre-detonation (engine "Knock") caused by compression or hot spots in the combustion chamber. If you really want to know if your car is running right on a particular grade of gas, look at the knock sensor counts...because that is what is going to retard the timing.

If you are still getting engine knock on a higher grade of gas, try swapping to a colder sparkplug (The leftover heat in the plug tip might be detonating the mixture before the spark even fires.)

I ran 93 in my L36 when it was N/A because due to the timing it had it needed 93 octane to not get KR. For most stock L36'* though, I'd just run 87 octane. Shouldnt' have any issues.

Well I know that even in my pre- series 1 3800, there is absolutely no reason to put in premium. I have done it, for a LONG period of time, and saw gas mileage actually worsen and of course NO power increase. Leave the premium to the forced induction engines and save some money.

Well yesterday I pumped in some plain jane 87 octane ARCO. I didn't even bother with the MMO either. I feel kind of guilty about the whole thing. :(

I noticed about a 20% drop in low end torque by going to 87. I'm going to try 2 oz. of acetone in it tomorrow and see if I can't regain the lost power.

You didn't notice a drop in power. There is no power difference between 87 and 91. One is harder to ignite. No other difference at all.

If you have KNOCK, you have issues you need to fix, rather than using higher octane. Your car should run perfectly on 87 octane.

What about the notion of the PCM advancing the timing (less KR) with an increase in octane? I've heard that speculation numerous times on the board.