COVER-SHIPPING 1172927 - Caterpillar

Caterpillar Machines Powered By 3500 Diesel EnginesSUPPLEMENT: 12/18/95Service Magazine; May 16, 1994; Page 14; "Fuel Dilution In Engine Oil"Under"CORRECTIVE ACTIONS TAKEN TO MINIMIZE FUEL DILUTION", the information after the last bullet (*) is not correct. The correct information follows: *If an engine application does not allow and engine idling extensively to be brought to full load and run at operating temperature, and fuel dilutions of the engine oil is present under these operating conditions, it is recommended the engine be shutdown instead of allowing it to idle. This will help reduce fuel dilution of the engine oil, reduce unneeded wear on the engine, and improve fuel economy.
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This information in this article is specific to Caterpillar machines powered by 3500 Diesel Engines only. In this article, any reference to engines is a reference to the 3500 Diesel Engines in Caterpillar machines.
The 3500 Diesel Engines in Caterpillar machines have a unit injector design, which requires lubrication at the upper end of the plunger and barrel. Lubrication is needed to minimize plunger and barrel wear, as well as to minimize possible seizures. This lubrication of the plunger and barrel comes from the fuel, which must reach the upper end of the plunger and barrel; in doing so, some of the fuel leaks to the crankcase. Therefore, it is normal and expected for these engines to have some degree of fuel dilution. The degree of fuel dilution largely depends on the condition of the injectors and the application and/or loading of the engine.
It is this degree of fuel dilution that needs to be monitored and may sometimes be a high enough concern to be further investigated.
See Caterpillar's publication, "Oil and Your Engine", SEDB0640, for additional background and reference information.
How Much Fuel Dilution is "Acceptable"?
The Caterpillar limit for "excessive" fuel dilution in ALL Cat engines is 4 percent. This includes the 3500 Diesel Engines in Caterpillar machines. If the amount of fuel in the oil reaches 4 percent, the oil should be changed and the source of "excessive" fuel dilution should be found and corrected. Logically, the lower the amount of fuel dilution - the better. The Caterpillar fuel dilution limit has been derived from a combination of internal testing, actual field experience, as well as an oil viscosity blending equation. The primary concern is oil viscosity. An example of this effect is a 5 percent fuel dilution of a new nominal SAE 40 oil will reduce it's viscosity to the next lower viscosity level (equivalent of SAE 30). Caterpillar experience indicates that fuel dilution below 4 percent does not reduce engine or bearing life.
Fuel dilution may be determined by SOS testing. Caterpillar employs ASTM D3828-A "Standard Test Methods for Flash Point by Setaflash Closed Tester" for the determination of fuel dilutions of 4 percent or above.
Possible Affects Of Fuel Dilution
The primary concern with "excessive" fuel dilution is maintaining a safe oil viscosity. Excessive fuel dilution (above 4 percent) can "thin" the oil to the point that reduced oil film