Diesel oil always 15W40?

[Red9654]

Being new to the world of diesel and on my way to become a diesel marine tech I've noticed most diesel engine oils seem to be 15W40 weight oil. is there a reason for this weight?

 

[alldodge]

IMO the diesel uses this do to the extreme pressures and loads placed within the engine. From small to the very large all use the same oil basically. Good enough flow when cold and sufficient when hot

 

[rbh]

Look in your owners manual, outside temp makes a big difference.
Some diesels will last longer if you run 30W in the summer because of the heat, but changed over to 15/40 for early spring, fall, winter.

Fuel is the same there is summer fuel and winter fuel (but I doubt you will be boating when the fuel will jell)

 

[Howard Sterndrive]

Caterpillar is a big player in the world of Diesel engines and they haven't spec'd 15W40 for 15 or 20 years.

 

[Sea Stomper]

Cummins recommends 5W30 in cold weather operation.

 

[HT32BSX115]

You won't go wrong with either straight 30w or 15w-40. If you like synthetics, 0w-40, or 5w-40 is fine too. Just ensure that the oil meets the required (and recent) API designation for diesels. http://www.api.org/certification-pr...iesel/Publications/MOM_GUIDE_ENGLISH_2013.pdf