A selection of molybdenum-containing, oil-soluble friction modifier additivas were tested comparatively in engine dynamometer tests on gasoline and diesel engines; the tests measured variations in brake specific fuel consumption with speed. The results indicate improvements ranging from 3% to 5%.
A similar selection of molybdenum-containing additives were evaluated in terms of transmission efficiency in a hypoid-gear, rear-axle test rig; the baseline oil was a formulated SAE-75W gear oil. Improvements in efficiency averaged 1-3%.
Bench-scale friction tests utilizing the Press-Fit, Timken and Four-Ball test devices were employed to establish a correlation between small-scale rigs and full-scale engine tests.