bad S4

I race an SCCA ITA Honda CRX and I wondered if I could use the extra 100 Octane Fuel in my 928.
At almost $6.00 a gallon I would like to use it since the racing season is over for me.

Bad S4
87 S4
Blk/Blk
5-Speed
28K Miles

shaaark89

really no reason to use it if the motor is anywhere near stock. higher octane will prevent detonation by burning slower, so unless you're running high amounts of boost or higher than stock compression it would be of no benefit.
on the other hand, it shouldn't really hurt it, so if it's just laying around.....

mark kibort

Nah, it will hurt unless you can take advantage of the higher octane by increasing spark or compression ratios. (which we cant in an S4)

generally, there is no need to run anything but pump gas, and running 100 may hurt power, as it has less of an energy factor

Mk

Sharks

Be careful with the 100 octane fuel. I use to work at a small airport, back longer than I want to remember now, and we had a student fill a plane that took 80 octane with 100 octane. I siphoned the 100 octane out and into my gas tank ('76 Firebird 400). When you are at speed the engine runs fine, but when you get to idle the engine wants to stall. I would suggest that you mix the 100 octane with fuel that you usually use just to keep the engine running at idle.

Brent 89-GT

Make sure it is unleaded if you still have the cats on the S4. The 100 oct I buy at the airport for my high compression Buick engine is low lead. If you run leaded through the cats, it will ruin them and plug the exhaust.

Sounds like you know it wont help performance, you are just looking to use it up right? If it is unleaded, or you have a cat-less S4, just mix it half and half with pump gas. The car will run fine.

jayc67

It's low lead compared to other aviation fuels, but absolutely not low lead to the point where it is safe for catalytic converters.

Aviation Blue 100 Low Lead will ruin a cat over time. Takes a lot though, the occasional run down the dragstrip won't do it too fast.

Also remember it is a violation of Federal law to use aviation fuels in a car on public roads, since there is no highway tax levied against it, and if you are caught buying it at the airport by the authorities, you will have to provide proof it's for aviation use. It's sometimes possible to convince them it's for "off road use" but if you're pumping it into a car fuel tank you're in deep kimshee

It's technically illegal for an airport FBO to sell aviation fuel for any other use, but with the growth of the self serve FBOs it's harder to regulate.