High operating temperatures, reduced engine cooling and prolonged drain intervals contribute to oil thickening, heat retention and deposit formation. These heavy deposits can impede normal piston ring function; thus reducing fuel economy, lowering power output, and increasing harmful exhaust emissions and oil consumption.

High operating pressures and temperatures put a lot of stress on diesel engine oils. Turbochargers, high engine idle, and direct fuel injection reduce oil life. Engine oil temperatures run high, resulting in oil breakdown and deposit formation in critical lubrication passageways. Emissions devices like EGR increase the soot accumulation in the oil. These systems place a heavy burden on the oil and push its stability to the limits.

With high combustion heat, acid formation from fuel blow-by, and soot overload, engine oils suffer from corrosive attack and abrasive wear, which eventually damage engine components.

Diesels are extremely sensitive to fuel degradation. Fuel breakdown byproducts impede injection and increase deposit buildup, leading to heavy exhaust emissions and power loss. In high-pressure common-rail (HPCR) direct injection engines, high temperatures and pressures can cause diesel fuel to break down into carbon deposits more quickly. The result is poor performance and potential engine damage.