MSOIL HAS DOCUMENTED INCREASING LEVELS of fuel contamination (fuel dilution) in the engine oil of 2007-2008 light-duty Ford, GM and Dodge diesel pickups, and indications are that 2009-2010 models are also affected. Research indicates fuel dilution is intensifying due to the use of in-cylinder post-fuel injection during the engine’s exhaust stroke to regenerate the diesel particulate filter (DPF). Fuel in the oil reduces the oil’s life expectancy and effectiveness. Because diesel fuel is a natural solvent, fuel dilution in motor oil causes a decrease in viscosity which may lead to an increase in engine wear rates.

Although AMSOIL Premium Diesel Oils have shown the ability to maintain integrity under fuel dilution conditions, the abnormally high rate and unknown long-term effects have forced AMSOIL to adjust its drain interval recommendations as a precautionary measure in 2007-2010 Dodge 6.7L, Ford 6.4L and GM 6.6L LMM light-duty turbo-diesel pickups. In these applications, AMSOIL recommends changing AMSOIL Premium API CJ-4 Synthetic Diesel Oils (DEO, DME) at the manufacturer-recommended drain interval. Drain intervals may be extended further with oil analysis.

AMSOIL previously announced a fuel dilution issue in 2007-2009 on-highway Caterpillar C13 and C15 engines that forced the company to adjust its drain interval recommendation in those applications to the manufacturer-recommended drain interval.

In all other applications, AMSOIL full synthetic diesel oils are recommended for three times (3X) the OEM recommendation, not to exceed 50,000 miles/600 hours or one year, whichever comes first, while Synthetic Blend 15W-40 Heavy Duty Diesel and Gasoline Motor Oil (PCO) is recommended for the longest OEM recommended drain interval. Drain intervals may be extended further with oil analysis.

For complete, updated AMSOIL diesel oil drain recommendations, see the Revised Diesel Oil Drain Interval Recommendations. For more information on the diesel pickup fuel dilution issue, see the Fuel Dilution Issues in 2007-2010 Light-Duty Turbo-Diesel Pickups Technical Service Bulletin (72k PDF). For more information on the Caterpillar C13 and C15 fuel dilution issue, see the Fuel Dilution Issues in 2007-2009 On-Highway Caterpillar C13 and C15 Engines Technical Service Bulletin (54k PDF).