In the United States heavy duty trucking lubricants market, the drive for energy efficiency is influencing a transition from SAE 15w-40 diesel engine oils to those with lower viscosity grades such ...

Best is 10w40 or 15w40 semi synthetic. After 10 years of bike use, I used 15w50, which is more viscous. I used this just for once to help remove deposits from engine parts.

76 Firebird Heavy Duty EC 15W40 engine oil from ConocoPhillips has been upgraded to meet lubrication requirements of the 2007 and later model year, low-emissions diesel engines equipped with ...