A caution note about using synthetics in an older diesel engine..If you really want 10w40, Shell make Rotella T5, a more expensive synthetic blend, in 10w40. I can see the advantage being easier starting on very cold days, and you're in a colder climate than me.
I never suggested using a synthetic, I suggested a synthetic blend. There isn't enough synthetic in a blend for the engine to care at all, but it's the only way to get a 10w40 without use of lots of viscosity modifier.
I agree. Shell Rotella is one of the few remaining fleet oils that have both a CD and SM ratings. I have six gas engines and two diesels. I buy Rotella 15W40 and run it in everything.All I can say is, I've been using Shell Rotella T 15w40