This paper describes the engine test and extended oil drain field performance of new synthetic engine oil technology developed for use in North American low-emission heavy-duty diesel engines. The resulting formulation utilizes an advanced additive system specifically tailored for synthetic base stocks which exceeds current industry and engine builder targets in critical performance tests. Use of synthetic base stocks allows the formulation of engine oils with a unique combination of performance characteristics, which include meeting SAE 5W-40 viscosity requirements for cold starting benefits while maintaining low volatility loss at high temperature for oil consumption control. In addition to meeting API CG-4, CF-4, CF-2, CF, SH and EC requirements, this technology has also demonstrated exceptional performance in extended-length diesel and gasoline engine tests. Furthermore, it has also performed very well in extended service interval field tests. At drain intervals up to four times those normally recommended, excellent engine wear, deposit protection, and oil consumption control have been consistently demonstrated. Additionally, fuel economy benefits in excess of 4% relative to SAE 15W-40 conventional mineral oils have been documented.