Another Oil Question 5w-40 vs 15w-40

[jimmy braden]

unless you really love the way it starts on the T6 i would just stick to the conventional. Or maybe a blend but still 15-40 Unless you run it in canada a lot.

[dennis45]

Originally Posted by jimmy braden

unless you really love the way it starts on the T6 i would just stick to the conventional. Or maybe a blend but still 15-40 Unless you run it in canada a lot.

Ya, having lived and driven on both sides of the 49th I can tell you that as soon as one heads north and crosses the 49th parallel, all bets are of. We need highly specialized oil here in the great white north. I think it must be the rise in altitude, not sure. But as soon as one heads south into say Montana, everything goes back to normal. Why is that?

[ftodaro]

Originally Posted by pete5016

Once again..BOTH Weights are recommended by Cummins. However, the 15W-40 is the "Preferred" Oil. That "Preferred" status is from a 2008 document.

Again, it appears that retailers are carrying the 5W-40, and appear to be dropping the 15W-40.

It appears that the "industry" is gravitating towards the 5W-40 weight (at least in the Synthetic).

SO - MAYBE A BETTER QUESTION:

What would you use - 15W-40 (T4 - Conventional) OR 5W-50 (T6 Synthetic)?

Thanks again.....

I split the baby, I use T-5 15-40 blend.

[Domo]

You have a 12 year old rig that has been just fine using manufacturer recommended fluids - why would you want to change?

Perhaps it's a philosophical question you've posed?

[96 Wideglide]

Originally Posted by dennis45

Ya, having lived and driven on both sides of the 49th I can tell you that as soon as one heads north and crosses the 49th parallel, all bets are of. We need highly specialized oil here in the great white north. I think it must be the rise in altitude, not sure. But as soon as one heads south into say Montana, everything goes back to normal. Why is that?