Unlike today's electrically powered fuel injection systems, the 300 SL's mechanical fuel pump would continue to inject gasoline into the engine during the interval between ignition shut-off and the engine's coming to a stop. This extra fuel both washed away the oil film critical to an engine during start-up and led to oil dilution, leading to excessive ring wear and scouring of the cylinder walls. Exacerbating the problem was the engine's racing-oriented dry-sump lubrication system, with its large oil cooler and enormous oil capacity, which virtually guaranteed the oil would not get hot enough on short trips frequently taken by most car owners to flow properly. Owners might block off airflow through the oil cooler and stick rigidly to the appropriately low recommended oil change interval. An auxiliary fuel pump provided additional fuel for extended high-speed operation or cold starts, but overuse could also lead to dilution of the oil.