Diesel engines in trucks are usually operating at more nearly constant speed and higher load factors than gasoline engines. Thus, combustion conditions are more nearly optimum, and water condensation and fuel dilution are not as serious problems. Where excessive fuel dilution occurs, it is usually the result of a mechanical problem, such as a faulty injector or defective turbocharger. Diesel fuel is not as readily evaporated from the engine oil as is gasoline; thus, if a problem exists, the concentration of diesel fuel will tend to increase steadily. This can lead to deposits and a reduction of the oil viscosity sufficient to promote mechanical wear.

Many large diesel engines in marine industrial facilities are operated on residual-type fuels with sulfur content in the 2–4% range. The sulfur in these fuels form extremely corrosive sulfuric acide which cause high damage to rings and cylinder liners, they increase wear rate and replacement inteverals of metal components and thus increase maintenace costs. Selection of Steel Shield Diesel Engine Oils becomes critical to reduce maintenance costs and downtimes.