| Mercedes uses high compression ratio motors in order to get maximum power out of minimum displacement. This involves more advanced spark timing than in a lower compression ratio motor. Premium fuel is required to prevent pre-detonation of fuel in the combustion chamber (knock).
If you use lower octane fuel the engine's knock sensor will detect this and will respond by retarding the spark timing to compensate. This will result in less power.
I can't say if you will be causing damage to other parts of your car by using regular or mid-grade fuel, I just don't know. But for the $20 a month difference between using premium and regular (thanks for the breakdown, GlennSter) wouldn't you rather just enjoy the car working as designed by the manufacturer? I don't think you'll save any money in the long run because the car will have to work harder to make the same amount of power. Working harder uses more fuel. It might end up being a wash, or it might end up costing you more. |