Effect of Piston Deposits, Fuel Sulfur, and Lubricant Viscosity on Diesel Engine Oil Consumption and Cylinder Bore Polishing

The purpose of this paper is to define the factors which affect oil consumption and cylinder bore polishing. The investigation focused on top land deposits, fuel sulfur, and lubricant viscosity in a series of direct-injection diesel engine tests in the U.S. and Europe.

In these engine tests it was demonstrated that excessive top land deposits cause high oil consumption and cylinder bore polishing. Cylinder bore polishing can also be caused by corrosion when high sulfur fuels are used with oils of low alkalinity values. Maintenance of the Crosshatch honing pattern is critical to oil control, low ring wear, and prevention of ring scuffing.

Low oil consumption and low cylinder bore polishing can be achieved with lubricant formulations which minimize the top land deposit and provide sufficient alkalinity to minimize the corrosive aspect of bore polishing.

In addition to the top land deposit and fuel sulfur factors, multigrade oils showed a significant oil control advantage in certain engines; and a theoretical explanation of this phenomenon is presented.