I recently saw racing gas being offered at a gas station and wondered if adding 1 or 2 gallons of this to a tank full of premium gas would hurt or improve anything? Can anyone offer some insight?

 

I would say no more then 3 gallons to a tank of premium, you will notice a difference. Go much hotter and you'll get into valve guide problems.

 

It won't makemuch of adifference if not worse.. I've run 110 in my M3 on the track and I have upgraded software on that car and it madevery little to nodifference. If a 98 octane is available that may make a small difference, most tracks offer this and 110. Make sure it is not leaded.

 

Here in Colorado, we used to be able to buy 93 octane, truck really well. They no longer sell that now, 91 is as high as it goes and after a couple tank fulls I can tell you, it did make a difference, I lost some power as well as mileage.

 

If I remember correctly, anything over 104 is leaded. Can anyone corroborate this?

 

I think you are right. everything i have seen was leaded, but that don't make it for sure.

 

I'm pretty sure anything over 104 is leaded.

 

I know what you're thinking and I like it [8D]. However, it would be a waste of money. Tetraethyl lead is used as an octane enhancer in aviation and some racing fuels. If it is present in the fuel you're considering, it will foul your catalyst.

It also might be worth mentioning that octane isonly a measure ofthe fuel'sresistance to ignition. The higher the octane, the harder it is to ignite it. Higher octane (racing)fuel is only needed for engines that run high compression pistons or with forced induction such as a turbo or supercharger. In such cases, the detonation margins are lowerbecause the heat of compression can be enough to 'pre-ignite' the fuel before the spark plug does the job.Octane has nothing to do withthe fuel'senergy content, though this is a common misunderstanding.

Confusing the issue further is the fact that modern engines incorporate knock sensors which will retard theignition timing (with a commensurate reduction in power output)if they sense pre-ignition occuring. This protects the engine from thecheapskate that runs 85 octane gas in a high compression, 91 octane engine. However,if you're running the recommended octane fuel, stock pistons and heads with stock compression ratios, your engine isnot goingto experience pre-ignition, even with a performance chip in an M3under racing conditions. The laws of physics are everywhere the same, and there simply isn't enough heat in the compression process to ignite the fuel prematurely.

In other words,running racing fuel is throwing money away for these engines. You won't get any more power than you will with 91 octane. Run the minimum recommended in the book, and you're good to go.

Dave