Earlier this summer I pointed out that Amsoil had released a notification that there had been a change in their interval recommendation on the oil filter for a certain Toyota engine.  Well, there is another change in diesel oil intervals in some trucks due to the contamination these engines are putting into the oil weakening the oil at a much more rapid pace than other diesel applications using the same oil.  This time it involves the Amsoil Premium CJ-4 Diesel Oils used in 2007-2010 turbo diesel pickups (Ford, Dodge, and GM).

It wasn’t long ago the intervals were raised to three times the normal intervals as this newer oil in the diesel line had proven itself, but as more analysis tests have come in, there has been a high amount of fuel contamination due to the purging, or regeneration, process performed on the diesel particulate filter (DPF), which involves pumping additional fuel into the cylinder which can get past the rings and into the crankcase.  While the oil is remaining stable, as a precaution, Amsoil has changed their drain intervals for these vehicles using this oil back down to OEM recommendations unless oil analysis is used.

Here is an excerpt from the Amsoil TSB I received:

OBJECTIVE:

Communicate the discovery and cause of excessive fuel dilution in 2007–2010 light-duty diesel pickups from Ford, GM and Dodge and the resultant reduction in the drain interval recommendation for AMSOIL Premium Diesel Oils in these applications.

ISSUES:

AMSOIL has documented increasing levels of diesel fuel contamination (fuel dilution) in the engine oil in 2007–2008 light-duty diesel pickups from all major vehicle manufacturers, and indications are that 2009 – 2010models are affected as well.

Research indicates that 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.

RECOMMENDATION:

Although AMSOIL Premium Diesel Oils have shown the ability to maintain integrity under fuel-dilution conditions, the abnormally high rate and unkown long-term effects have forced AMSOIL to adjust its drain interval recommendations as a precautionary measure for 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. The recommendation for these oils in gasoline applications remains 2X vehicle manufacturer recommendation.

Owners of affected vehicles should use oil analysis to determine the severity of fuel dilution in their vehicle. If fuel dilution levels are above 5 percent, contact the dealership or OEM for help finding a solution. AMSOIL and OIL ANALYZERS condemn oils with greater than 5 percent fuel dilution.

While AMSOIL does not have extensive documentation of fuel dilution trends for 2009–2010 models, it is safe to assume fuel dilution will remain an issue because these models employ the same DPF regeneration technology as 2007–2008 models.

Pre-2007 diesel applications not equipped with emission system devices are not affected by these changes. Those applications can still extend oil drain intervals to 3X vehicle manufacturer recommendation, not to exceed 50,000 miles/600 hours or one year.