Search Results

Nitrogen compounds present in mineral base oils at low concentrations are known to accelerate oil oxidation and to reduce the useful lifetime of formulated lubricants. Both Partial Least Squares and Neural Network analyses were employed to establish correlations between base oil composition and performance in industry standard thermal stability and oxidation tests. These correlations show that the “basic nitrogen” (BN) content of a base oil is a very important compositional feature determining its ultimate performance in a formulated lubricant which may be especially important for API Group II and III base oils that are relatively free of other pro-oxidants and naturally occurring, sulfur-containing antioxidants. The effect of BN species was also studied using model nitrogen compounds and it was confirmed that the pro-oxidant effect appears only in “basic” nitrogen containing molecules involving pyridine and quinoline derivatives.

A laboratory engine test technique has been developed to stress motor oils such that their relative high-temperature thickening characteristics in severe service can be predicted in a reliable manner. Engine mechanical condition, operating environment, and motor oil composition are important parameters affecting the thickening phenomenon. The mechanisms of oil thickening are complex and may involve nitrogen fixation or soap formation as well as bulk oxidation.

Piston ring wear studies using an automotive engine and a radioactive wear measurement technique are presented to show the effects of compression ring face metallurgy and general lubricant composition on corrosive wear control. These results are correlated with those obtained in a single-cylinder laboratory engine. Results show that lubricant com-position is not critical respecting corrosion when chromium plated and molybdenum-filled compression rings are used, but is critical when plain cast iron rings are used. Although wear for the molybdenum rings may be slightly higher than that for chromium rings, no service problems are anticipated.

The influence of lubricant formulation and service degradation on automatic transmission shift quality was studied in full scale transmission cycling tests. Fluid frictional degradation was found to follow a well defined pattern. This pattern is influenced by fluid formulation as well as transmission environment. Both fluid oxidation and selective additive degradation affect the rate of progression through this pattern.