chrisa_63

so I have a w211 E63 with a Weistec tune. I am going to the track soon and want to use 100 octane but all the posts about using 100 octane are confusing me so I have a couple questions about it.

1. Will using 100 octane on my car with my tune make a difference?
2. If so, how do I make a mixture of it? Or do I just put straight 100 octane only when I get on reserve? (I know, noob question but I don't want to mess my engine up so I'm being careful)
3. How long would it take my ecu to notice the different octane and adjust?

All these posts on here about it keep confusing me because many people say different things. I just want clear and simple answers. Looking forward to taking it on the track for the first time. Just ordered some 16" clk wheels wrapped in some Mickey's. Can't wait to see the results

sexyxe

Your car will need a tune to make best use of the added octane.
If you wanted a 100 octane tune, then running the minimum fuel to mix with is best. There are calculators available online to help with working out your new octane.
Your ECU wont 'realise' it has higher octane for normal driving, and under load unless the car has been experiencing knock before, and the new octane removes the knock, you wont really gain anything from it.

Hope that helps, and is accurate.

JoeJErnst

Higher octane gasoline will only improve performance if your computer is pulling timing due to engine knock. Whether or not that is happening depends on a lot of things, such as engine load, temperature, your tune, and, of course, gasoline quality.

So the short, simple answer is Yes, use 100 octane if you have access to it (make sure it's unleaded). It won't hurt performance, and it *might* improve performance.