2019 Ram 2500, 6.7 Cummins, towing a 10K fifth wheel in Texas. Cummins recommends 10w-30 above zero, REQUIRES 5W-40 below zero. I had dealer change the oil and use full synthetic. They used 5W-40. Is that ok for year around use with our hot summers? Is 10w-30 even available in full synthetic...

Jun 3, 2019 · I use 5w-40 as well and live here in hot South Carolina with my 2018 Ram. When you crank your engine the 5w oil gets to the parts faster than thicker oil. This is a big plus as you already know wear on engine start up is the worst. As the temperature rises you are protected with the 40 weight classification just as you are on the 15w-40.

Mar 2, 2023 · Most available 10w-30 is going to be a blend. 5w-40 is going to be full-syn. Most 15w-40 sold is conventional. I'd draw the obvious conclusion but it would be speculation. If deposits are the concern, it doesn't really matter what the factory fill is.

Sep 14, 2020 · In my experience with my 2004.5 truck, 5W-40 synthetic is fine for winter cold weather up here in Calgary where it gets to -30C/-20F. 15W-40 synthetic makes for a grumpy cold weather start. I would not recommend 15W-40 conventional oil for cold winter use.

Feb 21, 2023 · T6 5w-40 is a great oil and you’d be fine with it. I’m no expert on oil, but isn’t 5w-40 a thinner oil than 10w-30? And 5w-40 is better for the colder starts being thinner? I could be mistaken. Also haven’t seen any TSBs or anything in writing stating to use 5w-40 if you’re working the engine hard. Even though that gets stated a lot.

Jan 26, 2020 · Below about 60 degrees Frankenstein, 5W-40 is much thinner than 15W-40, so it'll help starting and provide better lube system flow in the first few minutes of engine operation (which is where most engine wear occurs). around 60 degrees Frankenstein, 5W-40 and 15W-40 have the same viscosity through the rest of the operating temp range.

Aug 5, 2021 · I run 5W-40 here in N. Idaho. The truck is quieter running the M1 ESP 5-40 than the 10-30 syn blend. Been running 5-40 for 20 years everything is still running.

Feb 25, 2011 · My owners manual says 15w-40 conventional oil, or 5w-40 synthetic. I ran the first 15k miles on conventional, then shifted to 5w-40 Rotella. I run the 5w40 year round, in hot Oklahoma summers, and (kinda) cold Oklahoma winters (well, it did get down to -6 this winter....). Seems either one will work.

Feb 28, 2024 · 5w-40 is better. Plus like gsbrockman said I don't really see 10w-30, maybe my last trip at the parts store, best price I can find is O'Reilly's through their website they always have a discount, minor but it usually brings it down a few bucks. You'll get oil pressure when starting due to the thinner cold weight, 5w.

Sep 28, 2009 · 15w-40 or 5w-40 Jump to Latest 14K views 18 replies 14 participants last post by salesrep Oct 27, 2009