Just a thought; My Kabota Diesel tractor uses 10-30 motor oil and sometimes works very hard on the farm. My Dodge/Cummings owners manuel calls for a variety of different weight motor oils. 0'-30'F calls for 10W30 weight oil. 10'-30'F+ calls for 15W40 weight oil. The thermostat regulates the running temp of the motor so why can't we just run 10W30 year around. What is the benefit of running 15W40 ?

 

i prefer rotella 15w 40 myself and i run in all type of weather and temperatures and i dont see anything wrong with it as long as u plug ur pickup in when its really cold but never had any problems with oil pressure in the winter i just love 15w40 its what ive always run in all my pickups just my thoughts on motor oil its more about what u prefer to pay for

 

How much 0 degree weather do you get in Alabama?

If not a lot, youll be fine with 15W40. Whatever you use make sure its oil that is rated for a diesel. Regular oil cannot deal with the soot generated by a Cummins.

 

i run rotella 5w40 syn in mine. year round. advantages to it in the summer you still have the warm up thinkness needed for thermal breakdown, and during the winter its still not so thick that if you forget to plug it in or cant, it wont take forever to build oil pressure. well i run it it my VW jetta tdi as well, my cub cadet lawn mower, and ford tractor. and in my kawasaki atv. so im pretty sold on it and its capabilities.

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im not so sure it ever gets to 0 in lower alabama. cause we never even see 0 in north GA. but the past few weeks it has been cold. but not that cold

 

Remember that you block heater does not warm up your oil, only the coolant. The oil is about 5" away from the effects of the block heater. The oil is still just as cold as the ambient temperature. Trying to suck up 15W40 at 0* is very difficult, and will take a while to get pushed though the engine. Until oil pressure is generated, and even a little after, the valve train is left with only the oil residue from when it was last run. 10W30 is better, but I prefer 0W40. I run it all year round, and we see temperatures from -40* up to +95*.

 

im gonna have disagree while agreeing with you on this, if that makes since. coolant runs throughout the entire motor, your heating the coolant with the block heat which in turn heats the cast block and head. metal tranfers heat energy very well and it will trasfer some of that heat to the oil pan its self, which will heat the oil in it above ambient temps. it wont get to coolant temps which is where i agree, but it will heat some which is where i disagree.

 

Heat rises, is that a good counter argument? Haha! Also, the gasket will act as a insulator between the block and oil pan. Unless all this heat is being transferred by the oil pan bolts. I think there would be minimal heat gains in the oil from the block heater working. Maybe a degree or two at the best. That's my opinion, I'll stick to running a lighter oil rather than hoping radiant heat will warm thick oil, allowing all moving parts to be lubricated quickly upon start up.

 

That oil is still pretty cold in the pan even with the heater. In response to the original question, you can either one all year. I know many that use 5/30 year round...although it's synthetic.

 

How about 10/30 all year around. Seams to me that 30W would circulate easier and more freely than a 40W

 

We get down to -20 or so in the winter so I run Rotella 5W40 synthetic in the winter and Rotella 15W40 in the summer.

Not to hijack but why isn't there a Rotella 15W40 synthetic? Just kinda something I've always wondered