I bought an E350 a week ago. Dealership says I can use regular gas. They say they use regular in their loaner cars. Manual says to use Super Premium (91 octane) and that an emissions warranty claim could be denied if MB could prove the problem was due to using less than 91 octane gas.

I'd like some comments from MB owners about using regular or super premium.

 

Like a dealer would denie a claim on themselves for the wrong gas. Plus they have no way to check what octane gas is in it all a dealer could prove was you had bad gas in it. So the only way they would know you ran 89 is you told them or left the slips in the car for them to read. Usally the better grade has cleaners in it how much would you save running the cheaper fuel? You bought class treat it like it

 

You're right. I'm going to use the 91 octane.