10w40 In Diesel?
 

Was wondering if 10w40 oil would work alright in winter temps. I figured 10 wieght would be thinner when cold and it should still have the 40 wieght when hot. Thanks for the help! :-wink

You need to look for the CH-4 or CI-4 ratings. These are the current diesel ratings. IMO you'd be much better served by a 5w40 synthetic diesel oil, like Rotella T synthetic. 10w40 has a tendency to cause sludge.

rusty70f100,
I am just curious as to why a 10w40 would have a tendancy to cause more sludge than other weights of oil? and also if this is true with 10w40 motorcycle oils?

A conventional 10w40 has more viscosity index improvers in it than most other oils. This is due to the rather wide spread. These shear down and can cause sludge. Motorcycle oils may not have this problem if they're synthetic, I dont know enough about motorcycle oils to give an accurate answer. However, synthetics have a naturally high viscosity index and do not need nearly the amount of viscosity index improvers.

We run Shell Rotella TSB 0w-30 in everything during the winter, with no issues at 242K's. We use 10-40 in the summer and run it in everthing gas-diesel.

Located over near Ottawa and it gets cold. The 0w-30 really helps cold start if no plug-ins are near.

Would there be any problems using a diesel rated 5w-30 or 10w-30 synthetic winter and summer in a 03 7.3 PSD? I've been reading where 10w-30 is being recommended for the 6.0.

I think you can't run the 30 for too long a period over 75 deg.F as the HPOP fuel system really beats the oil up (foaming) Up north of us where it is cooler in the summers some Cat service guys are telling the truckers they can stay with the 30 all year. Cat developed the HPOP fuel system and licences it to IH for the 7.3I have had to run to Florida in the winter and straight back -30 here 90 there and the 0w-30 looks real dirty at 2,500 miles but in the cold intervals are 6,000 mile changes and the oil looks comparable in color and texture. we use 10w-40 the rest of the year...

not very scientific..

I didn't know if the superior qualities of a good synthetic would offset the viscosity difference.

The important point is that the oil be rated for at least the minimum API rating called for in the owners manual. If the engine is very old it might be CC or CD, if new, CI-4.

Jim