Not the time to think about this. Most all MB models now take high test. Modern engines designed for high efficiency push the combustion process to the max. Turbo or Supercharging makes it worse.
The problem of low octane fuel is that preignition or detonation can destroy bearings and ring lands and burn holes in pistons. Higher octane fuels actually burn slower, more predictably.
Modern systems will actually retard the timing up to fifteen degrees by cylinder as knocks are heard and transmitted by the knock sensors. This means that the car will try to make up for the improper fuel. This saps the power so drastically that fuel mileage must drop. This poorer combustion does no good for the engine and carbons it up.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 04-30-2000).]