Older DD two cycle engines: The advice I'd repeat is to use a heavy duty straight 40 weight diesel lubricating oil, one recommended by Detroit Diesel which states "Detroit Diesel" on the container (along with other brand names). The key component for DD two cycle oils is less than 1% sulphated ash content. There are spec numbers which I don't have available, but which I have posted here over the years, but major oil brands like Shell Rotella, and Exxonmobil containers all state "Detroit Diesel" in writing (along with several other engine manufacturers). They are about 0.7% or 0.8% sulphated ash. The original MIL spec was 2104B which is now 2104F or maybe "G"... In any case, the oils must also meet CF2 designation and many now will say CF2/CF4 which is fine. Picking an oil weight is a compromise between cold weather starting and operation. The best solution is to use block heaters for coolant, immersion oil pan heaters and or keep your engine room heated during cold weather for appropriate lube oil viscosity during initial start. Then 40 weight oil performs as required. DD Bulletin 7SE270, "Technical Data Book-Lubricating Oil, Fuel Oil, and filter Recommendations" provides detailed specs. I have DD Engineering Bulletin No 38 Cold Weather Operation of Detroit Diesel Engines (mine is Rev 5, May 1989). It says that for cold weather starting, lube oil heaters "..should be chosen...for a final lube oil temperature of at least plus 30 degrees F. Higher lube oil temperatures will aid in quicker starting at low ambient temperatures..." Multiweight oils in two cycle Detroit Diesels are especially troublesome for turbo engines. I have posted details here previously but the bottom line is multiweight oils contain ingredients which foul turbos. Rob Brueckner1972 Hatteras YF _________________________________________________________________ Shed those extra pounds with MSN and The Biggest Loser! http://biggestloser.msn.com/