Fuel Contamination with DPF Systems

 DPF-Burdened Diesel Engines Are Fighting a Fuel-Contaminated-Oil Battle and LOSING !

It’s Time to Armor-Up Your Turbodiesel with AMSOIL.

Chart of Synthetic Diesel Oil Viscosity Performance at 4% Fuel Dilution

At 4% fuel dilution, AMSOIL delivered. The competition failed.

Diesel fuel is a natural solvent, and quickly reduces the motor oil’s life expectancy and effectiveness.  In diesel engine oil, a fuel dilution rate of 2 percent is abnormal and anything over 5 percent is excessive.  Fuel dilution leads to reduced oil viscosity, reduced oil film strength, increased engine wear (particularly in the cylinder/ring area), increased volatility, weakened lubricant detergency, accelerated lubricant oxidation, varnish formation, acid formation/corrosion and low oil pressure.

Factors such as frequent starts, excessive idling, short trips and cold starts have contributed to moderate levels of fuel dilution in diesel applications for years. But recent issues created by modern Diesel Particulate Filters (DPF’s) and other emissions management strategies have brought the fuel dilution problem to a whole new level.  For example, increasing fuel dilution levels are documented in 2007+ Caterpillar C13 and C15 on-highway engines.

In addition, the DPF regeneration process in 2007 to present GM, Ford and Dodge diesel pickups has also been identified as a major cause of troubling levels of fuel dilution.  Except for the 2011+ LML Duramax engines, all 2007+ OEM engines employ an “active” regeneration strategy that includes in-cylinder injection of raw diesel fuel during the piston’s exhaust stroke.  Some of the fuel is wiped/washed past the rings and directly into the crankcase, diluting the oil.  This periodic washing of raw fuel into the oil makes it even more prone to viscosity loss and places the engine at greater risk of abnormal wear.

AMSOIL’s premium CJ-4 Synthetic Diesel Oils stay within viscosity grade, even when diluted with 4% fuel – which has now become common in some vehicle conditions. Even though no oil can provide a decrease in your oil-dilution rates from regeneration over-fueling, AMSOIL CAN and DID provide superior protection for higher levels of fuel dilution than was previously encountered in normal diesel engine operation.  AMSOIL’s engineers understand the huge negative impact of fuel dilution problems on engine longevity due to DPF active-regeneration (as noted in the leading paragraph), so they made sure that AMSOIL’s diesel oils continue to maintain viscosity and other essential properties at higher fuel dilution rates, long after other oils have failed.

What oil’s in YOUR turbodiesel engine?  Here’s how to pick the best engine oil(opens in new tab)

(Published in 2009, the G2752 test report was archived due to one or more oils being reformulated, so that the performance results may have become inaccurate for revised formulations. However, the DPF active-regen fuel-in-oil problem is very real in diesel engines, especially when the truck is primarily a non-loaded commuter or idles extensively.  The report still illustrates AMSOIL’s history of superior lubricant engineering that provides a much wider margin of performance above minimum OEM requirements, which deliver valuable advantages under unexpectedly adverse conditions, preserving the life of your engine, transmission, differential.  Click link to open full G2752 test report in a new tab.)

(Brian Dobben – former OEM Headquarters Senior Engineer)

For detailed model-specific info on DPF engine oil fuel contamination, and other insider engineering tips for Dodge RAM, Ford, GMC and Chevrolet turbodiesel pickups…


DODGE RAM Cummins Diesel Owners Page
Ford PowerStroke Diesel Owners Page
Duramax Diesel Owners Page

UltimateSyntheticOil promotes the AMSOIL Filtration and Lubrication Gold Standards in the United States and Canada If you want to buy AMSOIL Products, visit our vehicle maintenance page, or the AMSOIL On-Line Store or download a clickable pdf e-catalog

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