<div class="htmlview paragraph">Extensive laboratory and field test data are presented on multigrade motor oils formulated with a new VI improver developed by Phillips Petroleum Company. This VI improver is a hydrogenated copolymer of butadiene and styrene. Its unique features are outstanding shear and oxidation stability, and excellent performance in Caterpillar 1-H diesel tests. Attention is focused not only on the unique features but on its overall performance in multigraded oils.</div> <div class="htmlview paragraph">Although this VI improver was originally developed for passenger car multigrade oils, data are present to show application in truck multigrade oils, high VI hydraulic oils, automatic transmission fluids, farm tractor hydraulic fluids, and use as a VI improver and thickener in several synthetic oils.</div>