Good to know, thanks. So, we need a rating of CJ or higher, correct?

 

Yes, if OEM emissions system are still onboard.

 

Majestic makes a 20W-50 that is CJ rated. Might be an option

 

That's true, in summer I really don't need the cold coverage of a 5 or 15W. I'll look into Majestic, among others. Thanks

 

Just curious, why the perceived need for 50 top weight oil? Are we seeing excessive wear rates with 5w or 15w40's?

 

Honestly, I'm probably perfectly fine with staying with the Rotella T6 5W-40, but with the summertime heat we get down here in Texas (triple digits) it might be beneficial to run an oil suited for the extreme temps. Just contemplating using something like a 20W50 synthetic during summer, then switch back to the T6 for other seasons. 5W-40 more than adequately protects against cold in winter here. Summer, on the other hand, can be like hell itself, lol...

 

Personally, and I ain't no expert, if these engines required a 50 weight oil for a severe duty schedule in high temps, it would be offered from the factory. You have big trucks running 30 weight oil, and while they do have lots more oil than our 6.7s, pulling 80k lbs plus puts a big strain on an engine and the oil in it...

but I could be wrong.

 

I don't have my owners manual handy, but IIRC they just provide the SAE oil temp range chart and suggest you use the oil for your operating environment (as do other manufacturers of vehicles). They have no idea where your vehicle will be operated, nor how or for what purpose.

I do follow maintenance procedures for severe duty operation, as I do operate in very dusty environments, as well as high heat (and tow loads on occasion). So, 5K oil changes, cleaning air filter every oil change, 15K fuel filters, etc..

However, I don't relish the idea of oil viscosity getting weak due to extreme temperatures where I do encounter my kind of conditions. Thus, the contemplation of an oil that's rated for those temperatures.

 

40 top weight oil is pretty stout stuff, if high temp is a real concern a PAO or ester based synthetic (Schaeffers, Redline, Amsoil boutique blended oil) is another option since those base stocks can handle high temps very well generally. That said I wouldn't think twice about tugging my 13k fifth wheel across death valley running my cheap TSC 15w40. There are enough UOA's out there of all types of diesels running single digit ppm per 1000 mile wear rates running 30 top weight, much less a 40 top weight oil that it is nothing I am concerned about.

The amount of CJ or CK rated 50 top weight oils is pretty limited and trading marginal (at best) viscosity protection could be totally offset, or worse, by the inability of the oil to handle soot at the levels a post-2008 emission compliant diesel and throw out. Sticking with the M1 15w50 example, a CF grade oil was introduced in 1991, the API says flat out don't use in a MY2009 or newer engine...

https://www.api.org/products-and-ser...l-c-categories



CJ and CK-4 oils were designed to keep most soot in suspension in the oil so it doesn't accumulate and cause blockages which are far more likely to happen with the older specs.

 

So, the long and short of it, is I should just stick to the Rotella T6 5W-40, for its other benefits. The 5W-40's highest rated temperature range is around what I'm encountering during peak summer, but I'm not exceeding it thankfully (man, I feel for y'all that live in Arizona and the Mojave).

Works for me. It was just mental contemplation and thought experiment at this time. On top of that, I religiously change oil and filter every 5K anyhow.

 

If high heat is the concern a synthetic 15w40, especially a PAO/ester blend ($$$$$$), is probably your best option, they have a slightly higher HTHS rating than 0w, 5w and 10w-40s per SAE J300 just due to the amount of VI required for the cold/hot spread compared to the tighter blends.



That said, elevated shear without accelerated wear rates is nothing to be concerned about IMHO. Honestly, T6 is a great oil that cover blooming near everything outside of the far edges of the extremes (artic and surface of Venus).

All that said I have 10w30 waiting to go in my truck for the winter. The idea people live where a 40 top weight oil might not be sufficient (and those places certainly exist) makes this New Englander sweat just thinking about it. I am as far south as I can go, too well insulated.

 

Agreed, if I lived that far north I'd have to consider those negative temps (for sustained periods), so don't blame ya. Extreme cold temperature is a much more considerable factor, for sure.

 

Sure we can get cold, but nothing like the states further north of here and MA, and in the northern territories of Canada. They get temps there that we get with wind chill ratings, what it feels like with the wind blowing.

 

Honestly, I am in SE Mass, it is flat out balmy compared to ski country New England, upstate NY, high plains and Canada.

I involuntarily spent two weeks in Black Canyon City, AZ in August of 2009 during a heat wave..... I have never experienced heat like that.... ever. To this day I am amazed our fifth wheel's AC didn't explode, I get it is a dry heat but so is an oven.

 

Upstate NY is in the mountains so yeah, would get colder than here in WNY. I live in south of Buffalo in the start of the hills, so it gets colder than Buffalo usually and warmer in the summer being further away from the lake. Yeah... I hear ya on the "dry heat" thing. I'd visit but sure wouldn't want to live there.

I'll never forget going to South Beach, FLA to visit my cousin back in my partying days for Halloween weekend. Could not believe when I walked off the plane when the moist heat hit after boarding the plane in Buffalo with the cool fall temps...