On Mercedes-Benz vehicles equipped with an engine oil level sensor, the instrument cluster may indicate that the engine contains too much oil. This may indicate fuel contamination in the oil.
The vehicle may be mainly driven in the city or used in frequent short trips where normal engine temperature might not be reached. With frequent cold starts and short trips, fuel can enter the engine oil in non-combusted condition.
Fuel out-gassing through crankcase ventilation is only possible once normal operating temperature is reached. If operating temperature is not reached, the fuel collects in the engine oil which in turn leads to an increase in the oil level, which reduces oil viscosity.
Reduced viscosity can cause engine timing malfunctions and the lubricating characteristics are reduced.
On vehicles that are primarily used for short trips, the engine oil level should be checked on a regular basis. If required, drain the fuel tank and replace the engine oil and filter.