Chevron Research Company and Detroit Diesel Allison (DDA) conducted a cooperative field test to determine the performance of SAE 15W-40 multigrade oils in two-cycle engines.The field test utilized 42 new 8V-92TA engines in new Kenworth trucks. A unique aspect of this field test was that all the engines had premeasured piston rings and cylinder liners. The latest DDA fire ring designs were also incorporated.There are three significant conclusions: 1. Grooveless fire rings provided 35% lower wear than the current grooved design. 2. Properly balanced SAE 15W-40 multigrade oils provided satisfactory service. 3. Sulfated ash in the range of 1.0% to 1.85% had no significant effect on exhaust valve deposits.