mAMG

Hello

I have been wondering what fuel type I should use ...

I have read here in forums, and people seem to use 91 premium or 93 premium (if available) in US.
Also read that some engines ECU is tuned for specific octane number, and some are adjustable automatically to the octane number you provide.

Here the types available is 91 Octane, 95 octane, and 98 octane, I have been using the 95.

What is the correct octane number that does not harm the engine , and provides the maximum performance ?

Thanks

Hulk

If the car is stock you should use whatever hightest octane at the pump, if it is tuned you need to know which fuel it is tuned for because if you use a 91 oct but tuned for 93 oct then the engine will knock or possibly detonate.

mAMG

Well it looks stock to me, don't know what octane it is tuned for since it is imported from Japan.

Also, how I can check for that knock ? At least I would be able to know the correct octane type once the knock disappear ?!

Hulk

If not tuned put in 91, not worth spending for more octane if not tuned for it
Can you ask the person you bought it from?

mAMG

Nope unfortunately I can't contact him.

So if I used 98 octane, is there any harm or drop in performance ? (Engine knocking or detonation)

Hulk

No problem with 98, if not tuned for it will make the car run richer and there will be no knock but you will also run slower since your afr is rich

Get tuned on a dyno for the octane you want, way easier

Shadow5501

It depends. What is the octane rating method used in UAE?

If it is RON (same as Europe) you should use 95. That is the commonly available grade throughout Europe and is what MB engineers their cars to run on.

In the USA we use (R+M)/2, known as pump octane. The 95 RON maps to 90 point something pump octane, so MB says to use premium in the US. That's why the guys above told you to run 91, but I don't think they are aware of the different rating systems.

Hulk

Yes , you are right, RON would make a diff, in that instance do as he says and use 95