PS.. you can run 15w50 just fine, your truck would love it especially if you tow or have a heavy foot. The 7.3 ain't too hard, the 6.0 would sheer it much faster.

Just about everywhere. You might have to ask for it if you don't see it.

 

I thought this was a diesel forum? Anyways I prefer rotella t but dont want to conflict with any international relations while buying my motor oil

 

I'm glad I read this, i used to think rotella was the best. Last oil change I got dello 400 le because of the stamp on the front, stating it rivaled synthetic. I have seen that mystic stuff at tractor supply and thought it was a cheap off brand oil. Ill try that stuff next time. Thanks guys.

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I am sure I could run it and the film strength of a 50 weight sounds nice on the rotating assembly but might be a little thick in the rails for me. I think I will stick to a 10w-30 in the winter and 15w-40 in the summer. I don't have a heavy foot and I only tow a few times a year, the truck really gets worked during snow storms and that is about it.

 

Have you tried 5w40 Rotella for winter?
Really good stuff!

 

I ran it in my Cummins, not my PSD. But my father has run it in his truck before (basically a clone of mine) and it worked well. But for the money and the colder weather performance T5 10w-30 CCV was pretty close for like 6 bucks less a gallon so I went with that. If I lived in an area that was below zero more often I would have gone for the 5w-40 but SE Mass doesn't get that cold.

 

Very true.. it does cost a premium.
The 7.3 is pretty easy on oil, not like the cummins is, but have you considered running an oil that is a heavier weight at temperature?
Whether it be a 5w40 (synthetic) or a 10w40.
A 10w40 diesel oil would give you the same cold-start performance with added film strength.

I understand there are a lot of guys running 10w30 these days, especially in the 6.0L (it likes to sheer oil down to 30w) but starting with a 30w would make me a little nervous.
The oil analysis reports on Rotella 10w30 look really great, but with such a heavy rotating assembly a *w40 oil would give me peace of mind.

 

Running a 30wt doesn't get me too nervous, FoMoCo claims on the 7.3 it is the recommended oil under 30*F and on the 6.0's manual (updated for at least CI-4 oil) it says you can run it up to 90*F, which is most of the year where I am. My father ran Amsoil's 10w-30 for the first 100k or so he owned his truck and never had any issues and I only run it in the colder weather...my next oil change should be in late Feb or early March so I will be changing it over to 15w40 for the spring/summer. Strictly based on cost, no fear of additional wear in the heat. I have read too many good UOAs on many different vehicles running 10w30s in much harsher conditions than mine to be nervous about excessive wear. The 6.7 PSD specs a 10w-30 from the factory nowadays so I think in the future with fuel economy becoming a bigger and bigger issue to fleets I think you see more 30wts.