[NYG]

I have the B58 with the MPPSK flash/exhaust and I'm going to take my car on a circuit pretty soon. I was wondering if any of you guys can give me some advice as to whether 100 octane would compliment the compression ratio of the engine or if I'd be wasting my money or possibly damaging the engine. I don't really expect the latter but who knows.

Thanks

[upsidedownfunnel]

You wouldn't damage your engine but you probably wouldn't gain any power assuming you're normally filling up with 93. The stock tune is fairly conservative to begin with (even with MPPSK). To see any actual gains, you'd need a tune that could take care of the more aggressive timing of higher octane gasoline.

[BEAR-AvHistory]

Could help if the engine heats up while running. Will put off knock better then 93 under high heat, high load.

[NYG]

Originally Posted by BEAR-AvHistory

Could help if the engine heats up while running. Will put off knock better then 93 under high heat, high load.

Hard for me to say, the last time I ran the car really hard my oil temps didn't jump at all. Only thing that happened was my rotors got warped. Any experience running it in your B58M?

[Rebound]

You may even lose power. Octane is a property of the fuel to resist combustion. The fuel/air enters the cylinder, is compressed by the piston, and hopefully ignited by the spark plug.

If the octane rating is too low, the heat/pressure inside the cylinder can begin ignition too early.

But if the octane rating is too high, what can happen is the opposite, and combustion may not complete. Now, you'll still get combustion and the car will run just fine. But incomplete combustion will reduce horsepower and mileage.

Another issue, which I don't know much about, is that getting the higher octane rating is usually done with additives such as ethanol, and your engine may not like them; they could cause deposits or higher combustion temps.

Not to boast in front of a bunch of fellow BMW owners, but my other car is a Prius. I know, you're jealous. Anyway, I used to track mileage meticulously, counting gallons pumped and miles traveled. Sure enough, when I tried higher octane gas, mileage decreased. So this really is a thing, but of course, YMMV, depending on your engine setup, ignition timing, and the actual octane of the fuel.

[BMWILUVU]

I mix in 100 octane before getting on the track.

[Feddersen]

I am using 100 octane all the time and never had any issues. The higher the octane the lower the risk for misfires. The engine tries to "read" the quality and adjust timing to the octane level. I believe it even says so in the manual.

[jalkster]

I run it when I go to the track. But, I am tuned.

[NYG]

Sounds like maybe I'll try a 1/2 tank of 100 and take it from there. Appreciate all the replies fellas.

[BEAR-AvHistory]

Originally Posted by NYG

Hard for me to say, the last time I ran the car really hard my oil temps didn't jump at all. Only thing that happened was my rotors got warped. Any experience running it in your B58M?

Have not tracked the 440i B58M. Last BMW to be tracked was the 335is. It was run stock with 50/50 93/100 & drag raced JB4/COBB with pure 100. The COBRA replaced it & the 435i N55M I got at the same time went to second choice DD duty.

Its not oil or water you need to watch its the air inlet temperature. The B58 water cooled intercooler might be better but the air 2 air N54/55 would heat soak quickly. This generally required an aftermarket unit. I ran an ECS unit.

If you have scanning tool it can be useful to track that temperature to see how you are doing ambient vs inlet.

FWIW 100 is cheap insurance for a track day that will prevent an ignition pulls under load. I was getting mine at the pump in Cary NC for $7.10 a gallon at the time.

Its an incorrect urban legend that high octane fuel will go unburned & cause issues. Its also an urban legend that it will harm you car.

The only thing harmed is your wallet if you buy more octane then you need.

For DD & an occasionally hard moonshine back road run NC's normal premium @ 93 octane is fine. If I ever take it to VIR it will go on a 100/93 mix.

[simonelwell]

Biggest limiter on the track will be your brakes - rather than the fuel. Stock brakes, like mine, heat up and fade after about 3-4 hard laps. Short bursts and a cool down lap are the recipe...

[NYG]

Originally Posted by simonelwell

Biggest limiter on the track will be your brakes - rather than the fuel. Stock brakes, like mine, heat up and fade after about 3-4 hard laps. Short bursts and a cool down lap are the recipe...

I'm expecting it but they're not as horrible as I had initially expected. Can't wait for the ceramics on my M5C.

[chiefneil]

Originally Posted by Feddersen

I am using 100 octane all the time and never had any issues. The higher the octane the lower the risk for misfires. The engine tries to "read" the quality and adjust timing to the octane level. I believe it even says so in the manual.

Euro 100 octane is roughly 94 US octane equivalent.

[mike@x-ph.com]

No issues from using higher octane but you wont make any noticeable power unless you change your tune

[BMWILUVU]

The B58 high compression engine is octane starved especially with a tune.

[NYG]

Originally Posted by BMWILUVU

The B58 high compression engine is octane starved especially with a tune.

Made a new thread about my experience with 100 octane yesterday. It was fantastic.