Wow. Some bad advice in here. Its all about compression ratio, not performance. You may not hear it, but the engine can still have detonation, aka "pinging". Run what your engine calls for and go to Starbucks a couple less times per month to make up the "expense" difference.
On a Ford 4.6L VTech ANY pinging will quickly destroy the oil pump. It practically disintegrates! I am not sure if an MB engine has any issue like that though.
If one spends $150/month in fuel. Premium is less than $30 more a month. Not a bank breaking difference.
As for gas companies telling people to buy premium. Never happened. Again, octane requirement is related to engine compression ratio. Thats all. I am sure gas companies call it "premium" for a reason, because they sure make a huge premium on it. But I really recommend you use what you should for any vehicle.
Side note: Some people like to "treat" their car with an occasional tank of premium. Bad idea if it calls for low-octane. The higher octane needs more compression to start a flame front properly. So the car adjusts. Then when you switch back, it has to adjust again. The entire time economy is impacted adversely.
Another side note: Did you know E85 is 94-98 octane?