I use BP, Racetrack, Exxon, Cowboys, Chevron...whoever has the best price.

I run a 50/50 mix of 87 and 93.

I have done this on our Mercedes thru the years for over a half-million miles. I never use Seafoam or any cleaner. I have never had any ill-effects.

Gas is gas. It all comes out of the same pipeline and the various retailers add (or don't add) their additives.

I also use Supertech oil from the Walmarts. Because it's cheap and oil is oil, IMHO. I had to pull the pan off our '90 because a professional mechanic dropped a ball socket into the engine and it eventually locked up the oil pump. The inside of the engine was spotless - no sludge or buildup of any kind. The car was sixteen years old. The oil managed to stay in the bearings and even though I drove it probably two miles with ZERO oil pressure before I noticed (I heard lots of noise) the engine was not harmed. I was amazed.

Perhaps someone else can fulfill your demand to answer ALL the questions.

BTW, would you like to tell us which Mercedes Benz model you own?

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2012 E350
2006 Callaway SC560