Evaluation of Camshaft and Lifter Wear, Deposits, and Oil Thickening with Low-Phosphorus Engine Oils in Taxicab Service

A 160 000-km taxi test was run to determine the effects of low-phosphorus engine oils on engine durability. Camshaft and lifter wear, deposits, and oil-thickening were evaluated in thirty vehicles with oil-change intervals purposely extended to increase test severity. Three SAE 5W-30, SF, low-phosphorus (≈0.06 mass percent) oils and two SAE 10W-30, SF/CC, normal-phosphorus (≈0.11 mass percent) oils were evaluated.

Overall engine durability and performance was satisfactory with two of the three low-phosphorus, and one of the normal-phosphorus oils, and unsatisfactory (because of high wear) with the other oils.

These results demonstrate that low-phosphorus oils can be provided if further phosphorus reduction is necessary to protect emission control systems, and that current normal-phosphorus oils must be properly formulated to protect engines.