Hello there!

Guys I just wanted to make sure, on AMG's website, the fuel for the C63s is recommended to be premium unleaded. Well, the name they give it might differ from country to country.

I wanted to make sure on one thing because I've read several people writing that premium unleaded translates into 95 octane petrol? I always thought it that the C63s would need super (98 oct.) petrol?

Any takes on that?

In California "super" or premium is 91 octane rating. That is the minimum octane allowed for California c63s and the maximum that is readily available at gas stations. Other countries don't have to comply with California emission laws. You will see what type you need based on the info inside the gas door that should be specific to your country.

I see myself going for the 98 octane! If only I were to be in Germany then I would've filled up my tank with Ultimate (102 octane) xD !

Remember, octane ratings are different between the United States and Europe. I believe that 93 in the US is equivalent to 98 in Europe.

Based on this, the C63S will run best on 98 in Europe.

Look at the inside of the fuel door. Follow.

Ira is correct as Europe and a lot of the world uses RON (research octane number) and the US and Canada uses AKI (Anti knock Index)and it is as he says about 5 points lower if comparing in the US. So CA get 91AKI or same as 96RON and the rest of the US is 93AKI or 98Ron as in Europe.

Also, don't use a higher octane than is needed. Using a higher octane than is needed will lower performance.

In simplified terms, the higher the octane, the slower the fuel burns.

As an example. an engine tuned for maximum performance on 100 octane fuel will actually make less power using 120 octane fuel than it would it using 100 octane.

Ahhh, wise words. Agreed.
Mainly applies to older engines where only one or two timing options were possible. Managed engines self adjust and are able to some extent make the higher octane work for them. Imo.

Most premium gas engines in Cali market are tuned to aki 93 but are able to detune automatically to accommodate 91 as a small compromise.

Yep, there is a certain amount of flexibility built in.

I can't count how many times I've been at the track and overheard "It runs good on 93 octane - so I'm going to put some VP 109 in it" and then they scratch their heads when the car runs a slower ET and MPH.

I have learned to keep it to myself for this specific topic. That is why it was refreshing to hear from someone else.

Yes engines have for some time been able to sense octane and if you had to use 87 octane for example it would retard the ignition timing and keep detonation at bay.

thanks a lot guys! much appreciated.