Michael Khan

Sorry if this is a stupid question, but what is the highest octane level fuel we can use? I have always used 93 octane in my car but a gas station next to my work has 100 octane now.

whoover

The simple answer is that there is no maximum octane that you can use, only a minuimum. 100 won't hurt the engine.

On the other hand, since the stock ECU is tuned for 91 octane, anything higher is just a waste of money. It won't affect performance.

100 octane is great if you have an ECU tuned to make use of it. But if such an ECU tune is not switchable (or somehow can detect lower-octane and switch itself), you would be locked into using 100 octane. That's why 100-octane fuel is normally used as "racing fuel," for dedicated track engines that require it and are towed to the track by 91-octane engines.

Mandarin

I would agree with the previous reply. Will not hurt but won't help too, probably you'll get better fuel consumption.

If you have a tune you can use anything up to 105 Octane. Everything higher than 105 should be mixed with 100/93/92/91.

Michael Khan

Thanks Alot! Most of my friends who run 100 octane fuel always have it stocked in their garage at home. Was hoping that there would be some sort of difference in performance but did not know about the ecu tune.

wassup61

I've been running this since the first tank - Sunoco 260GT 100 octane unleaded - It helps that I have a pump down the street from me at 7.89 a gallon.

Usually, Bosch/Siemens ECM logic is able to respond with positive timing adaptation with a few points of Octane. That being said, we are all running relative high boost, and the 100 octane UNLEADED and OXYGENATED will add some added power and protection against timing pulls/spark knock

jkob5

I'm going to try and beat my stock time of 11.11 this Friday night with some race fuel. I know it's not tuned for it, but it should help timing stay advanced and who knows. 10.99 is the dream but I don't believe it's possible.

kponti

It does help, you can gain quite a bit of power with race gas (I went from 499 to 526rwhp on a W212 with race gas and 10 or so mins of driving).

The ECU will.adapt timing and boost (most likely advancing) to take advantage of the cooler burning of race gas. So some power to be had even when stock.

Clk63blkseries

100 octane is a waste of money if no tune. Does absolutely nothing and can cause the car to be confused and take back some timing to protect itself.

If you do use 100 use one of the street mixes. You need some of the additives in it for street car motors.

jkob5

I think you're right. My car that normally runs 11.1 at 125 just ran 11.3 at 118....not even in the dame ballpark in the trap. I had 1/4 tank of pump and I added 4 gallons of race gas 104 octane. Will not do again....