Things to avoid when operating a diesel engine on VO fuel.Even when petrodiesel is used as a fuel extended idling can cause accelerated piston ring coking. When VO fuel is used piston ring coking occurs much more quickly. Diesel engines tend to cool to well under full operating temperature when idled for more than 10 minutes. This is especially true when the air temperature is low. When this happens some diesel fuel tends to not completely combust and accumulate in a thin film on the combustion chamber walls. The piston also tends to shrink slightly and allow more blow-by than when the engine is at full operating temp. Since diesel fuel does not tend to carbonize in the ring lands nearly as easily as VO fuel the rate of ring coking during extended idle is nearly insignificant compared to when VO is used as fuel under the same conditions. Similarly when diesel fuel is able to leak past the piston rings and into the crankcase oil it merely dilutes the lubricating oil. In surprisingly small quantities VO fuel can polymerize the lubricating oil and cause it to turn to a jelly like mass that is too solid to provide sufficient lubrication to the engine to prevent catastrophic failure once the engine cools completely and is restarted.This is also the reason that extended oil change intervals are not a wise choice when VO fuel is used as a fuel. To ensure that a diesel engine enjoys its maximum engine life when VO fuel is used change the oil at (or more frequently) than the manufacturer suggests. The use of synthetic crankcase oil is not reccomended since these oils are engineered to provide adequate lubrication for longer than reccomended intervals. My reccomendation is use an inexpensive oil of the type designated specifically for diesel engines and change the crankcase oil at the "dusty condition" mileage/hours that the engine manufacturer reccomends.
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