impr

Apologies for the cryptic title, but recently I lent my tuned c63 to a friend who decided to do me a 'favor' by filling up down in the states. Currently I'm situated in Canada and always fill up with 94 octane, but I know down south the maximum octane is 91.

My tank at the time was about 1/2 filled with 94 and when I sent my ecu in for tuning I specified that I fill up with 94 octane. What I"m worried about is if the Eurocharged v3 tune i received could have been mapped only to 94 octane and as a result putting in 91 will result in knock/detonation.

Does anyone have any insight into this issue? or are my worries unfounded.

BK63amg

Where did he fill up? In the northeast U.S. we get 93 octane vs California where the best is 91.

I wouldn't be too concerned about knocking with 91 octane - combined with the 94 you had in your tank, you're averaging 92.5 octane (lol) which is close enough to 93 so you shouldnt experience any major issues.

Now if he would have filled your tank with 87 octane...that'd prolly be a different story!

PetroC63

I wouldn't worry, the difference in octane is minimal and the ECU should pull timing if necessary.

impr

edit: Called eurocharged, and they were extremely helpful. Pretty much nothing to worry about.