Originally Posted by JohnM.

That's true. Continual running of low grade gasoline is not good for the engine. Nowhere in the manual does it say that 87 octane is OK. It's not because Mercedes is trying to stick it to ya, these engines REQUIRE premium gasoline. Conversely, running 91 in your Honda when it only requires 87 is just as retarded.

Even though there is a knock protection system on these cars, there can still be detonation you are NOT hearing, causing engine damage!