101 Octane

[humpday]

My M4's been limited by 91 octane, so I decided to fill half my tank with some expensive ass 101 octane fuel just to see if there was a difference. I drove around for a bit, let the fuel "simmer" in the engine, warmed up my tires, then pushed it pretty hard.

At first, I thought "damn…this is awesome! It makes my car so much faster". Then after a couple other runs of accelerating hard - both from a crawl and from higher speeds - I though that the difference wasn't that great. In the end, I felt like the fuel made the car perform better, but certainly not something I would buy on a regular basis.

Anyone know how much, if any, of a difference there is with higher octane fuel? For all I know this could be all placebo effect!!

[ibimmer954]

Unless you have an aftermarket tune designed to take care of it, I seriously doubt there's much of a real effect there. BMW doesn't design their engine parameters for 101 octane.

On the other hand, depending on the mix, you are probably pushing your effective octane into the mid to high 90s. That might make a little difference.

[8600RPM]

As Temps rise you'll find more benefit

[carholic]

BMW did design the car for 93. Putting in 91 will reduce performance. I have ESS and I was told that their tune can take advantage of the octane up to 96. I mix my tank just to get to around 96. I can feel the difference easily.

[JustinCredibleM]

If you've been running 91, then you'll definitely notice a difference when switching to higher octane since you no longer have reduced performance. However, to get max benefit of higher octane, there needs to be a custom tune for it. But on the dyno, doing a baseline on 91, then one on a higher octane mix will yield a delta.

[apexit]

all the higher octane will do is let the engine run better/ smoother. Without tuning there wont be much of a difference and even then you'll want a tune to maximize the higher octane.

[8600RPM]

Does nothing for better or smoother. It prevents car pulling timing and thus keeps max power especially with warmer temps

[zosoboogie]

What about 98 octane at the track such as Sebring for a stock M4 would there be any benefit?

[Roadkiller]

Originally Posted by carholic

BMW did design the car for 93. Putting in 91 will reduce performance. I have ESS and I was told that their tune can take advantage of the octane up to 96. I mix my tank just to get to around 96. I can feel the difference easily.

Have you tried E85?

[AlpineE92M3]

All the octane rating is the resistance to detonation. Higher octane might trick the computer to alter timing but without a tune, you won't see any real difference. The sock tune is no where near tuned for 100+ octane.

[Tiago@VRSF]

You won't really benefit from higher octane gas without a tune

[8600RPM]

Yes you actually will. 91 and any heat will cause timing to be pulled quite quickly. So it will allow you to make full power. In e92, you couldn't hit full timing target with 93 in summer temps. It too needed 95

[Tiago@VRSF]

Anything above 93 octane will not show any gains on the stock tune. Race gas/high octane fuel will only provide you with knock resistance. There isn't something magical in the fuel, it's simply knock resistance

The DME doesn't read the higher octane gas and up timing. That'd be too easy.

If you're using higher octane fuel as a knock suppressant like your extreme heat example then you'll make the same power you're supposed to make, you won't increase HP on the stock tune.

[8600RPM]

It actually does. Since e46 M3 generation. It will advance timing progressively atleast on e46 and e92. It doesn't measure octane but pushes timing until essentially knock detectected. Many have logged this on past m cars

[CanAutM3]

Originally Posted by 8600RPM

It actually does. Since e46 M3 generation. It will advance timing progressively atleast on e46 and e92. It doesn't measure octane but pushes timing until essentially knock detectected. Many have logged this on past m cars

A good example of this is Dinan who was able to log a 11hp gain on an E46 M3 by simply going from 91 to 93 octane fuel: