98 octane fuel

[wannabeemer]

Here in Australia our unleaded petrol fuel comes in three grades, 91, 95 and 98 octane. The 135i is sold here with BMW's recommendation to use 95 octane fuel. Is the use of 98 helping your engine, fuel injectors at all or does it just give you more power for more $s?

[Matticus91]

Originally Posted by wannabeemer

Here in Australia our unleaded petrol fuel comes in three grades, 91, 95 and 98 octane. The 135i is sold here with BMW's recommendation to use 95 octane fuel. Is the use of 98 helping your engine, fuel injectors at all or does it just give you more power for more $s?

No need to run higher octane than specified unless you're hearing engine ping or have a tune.

[davis449]

No. 95 RON is the min. the car needs, which is equivalent to US 91 octane. Premium unleaded can come in several grades in the U.S. but the most common are 91 and 93 octane (so 95 and 98 RON). In this area of TX, 93 octane (98 RON) is 99% of premium unleaded available.

[jemfff]

Originally Posted by wannabeemer

Here in Australia our unleaded petrol fuel comes in three grades, 91, 95 and 98 octane. The 135i is sold here with BMW's recommendation to use 95 octane fuel. Is the use of 98 helping your engine, fuel injectors at all or does it just give you more power for more $s?

Strangely enough, in NZ it states min 98...

AU and NZ octane ratings are the same?

[ErvGotti]

There are three measurements of octane ratings used in the world. They're RON, MON, and AKI. The higher the octane the more resistant the fuel is to pre-detonation. This is especially important in turbo vehicles, due to the fact on really hot days when your intercooler is heat soaked, the hot air can cause the fuel to ignite prematurely.

If your car's stock you should be fine running the minimum recommended fuel, but if you mod I suggest running the highest octane available.

Most tunes for the N54/55 you see out there are using the american AKI rating. Such as MHD and Cobb. When they reference 93 it's AKI or 98 RON. Watch the video below it's very informative.

[Stubbie Blue]

In theory, the ECU should be able to adjust and run more advanced ignition timing and more boost on 98 RON to get a few more hp.

The manual for the US spec 135i N55 says 91 AKI recommended, minimum 89 AKI which is our mid-grade.

[wannabeemer]

Thanks everyone.
Strange that I'm not getting email notifications to your posts.