I am using ESSO 0w40 synthetic oil. The number 40 is the one which is important at high operating temperatures. I think you should be more concerned if you have a second number lower than 40. The first number has to do with how well the oil flows when cold- it has nothing to do with the oil being "thinner" when the engine is at high temperature. In fact, with a good quality synthetic oil, it should be useful to have a lower first number, because when you start your truck cold, the oil pressures up faster. The "lighter" oils at high operating temperatures are the 30 weight oils- eg. 0w30, 5w30, 10w30, or 15w30. 40 weight oils are recommended for the Cummins.

 

Changed mine at 38k with no leaks. I have noticed my engine runes smoother and my load at idle droped 2% (looked at the edge) I send my oil in for analasis but i have extended my oil changes

 

Thanks for the replys. Thinking about going to Valvoline Premium Blue Synthetic 5w-40, but i can't find it. One place , car quest can order it.

 

oil pan heater fixes that problem. I have mine hardwired into my coolant heater. So i plug 1 plug in and it runs both my coolant heater and my oil pan heater.

 

Use AMSOIL 5-40 Thats what i use. You talk about QUITE and SMOOTH! Dont get any better. Been in it sents new.

 

Going to switch mine on first oil change.....5500 miles....won't hurt a thing!

 

The oil pan heater is a good idea. What I'm saying is that even in the summer months, an oil with a lower first number will pressure up faster, which can't be a bad thing.

 

Can you prove or expand upon your comment that during summer months a 0 weight will pressure faster than a 15w?- don't forget it may be a 0 weight at a given temp but when it warms up the viscosity also increases to a higher number...
edit- I should have said that when warm the viscosity acts as a higher number-IE 40 weight at operating temp. It will always be more viscous when cold.

 

So, it is highly possible that your 0W40 say, at 80 degrees f may actually be thicker than a 15W at the same temp- all depends on the brand and the viscosity at a certain temp.

 

changed over to rotella synthetic at 10,000 miles. at 21,000 now with no leaks so far

 

anyone use shaffer, does it work well in these motors? [newbie to dodge]

 

Cummins Corporate website says it's OK to switch to full synthetic in these motors after break in period which depends on how you use your truck the first 10-20k miles. I switched at 15k to Amsoil. No problems.

From the Cummins website

Is it OK to use synthetic oil with my Cummins engine?
Cummins recommends that you not use synthetic motor oil during the break-in period. The Owner's Manual contains information on the type of oil that is recommended throughout the life cycle of your engine.

 

How many miles does the Cummins engine require for break-in?
In general, the engine requires 5000 miles for break-in. This depends on the type of driving the truck is subject to; hauling or towing a load will shorten the break-in period. Light duty hauling or "babying" the engine can delay full engine break-in for up-to 20,000 miles. It is best to avoid high engine rpm's during the break-in period.

 

Changed to Mobil 1 5W-40 at 22,500 miles. No leaks.

 

I am using Shaeffer's 9000 in conjunction with amsoil bypass filter. I am getting 20k oil changes. Oil analysis by blackstone labs says engine is doing very well. I have 120k miles.