The only reason I can come up with that makes any sense is that they really wanted to say full synthetic oil. What in the world would cold temp viscosity have to do with severe service towing?

Hoping for a logical answer. Not sure if this is all 6.7 or just the 2017...

 

All the 5W-40 oils that *I* have seen are full synthetic, therefore will stand higher temperatures. But other than that ?????

 

Probably because it is synthetic. It's not possible to have a 5-40 Dino oil (or that's what I've read) and cold weather performance combined with long lasting surface coverage is where it's at. My guess is when you get in the 50 range the cold pour is just too much for the internals on a regular oil.

I run 5-40 just so I don't have to worry about it when I travel north and west, and hot weather performance is still solid.

 

Synthetic also cokes less, what I've read, in high temp areas such as the turbo.

 

All I can tell you my 2016 6.7 when they tore into the motor at close to 50,000 miles the mechanic told me he couldn't believe how clean the top end was. According to him it look like it was a brand new motor always ran full synthetic after the first oil change even in my 17 nothing but synthetic it's not that much more money after visually inspecting the top end myself and the throttle plate not even a hint of coating I was quite impressed myself too bad the bottom end spun out but that's another argument take care

 

not trying to be a jerk or anything, but you are saying synthetic oil is good, yet your engine spun a bearing after 50k and had to be torn down while running synthetic? That would steer me away from using synthetic..I've always ran dino oil in everything and my engines are clean...

 

do a search for his posts/threads.....there are some oil spec issues.....CJ vs CK.

 

I run dino right now and really what keeps the motor clean is regular intervals in your servicing.


Far more important is to run the right oil for the weather and use of the truck.


Second is proper maintance and a good filter.


Maybe that is the other way around...you get the point.

 

The spun bearings are a known issue with these motors. Doesn't happen to a high percentage, but it does happen. Usually happens by 55k miles if it's going to. We had a 550 at work that spun one at 52k. Only used dino oil. So it's not the synthetic oils fault. Others who have had the same problem run various oils. It's not the oil.

 

Yeah didn't want to get into that discussion it had nothing to do with the synthetic oil many will tell you it's just a bad design without the little tabs which is absolute BS has nothing to do with why it happened shell t 6 change the oil formulation in my opinion months prior to the spin out in truck getting louder over 24000 miles of heavy work daily in less than seven months regardless of the spin out as I stated the the entire system spotless clean the mechanic said he's never seen that in a 50,000 miles 6.7 especially the throttle plate should be covered was spotless like it was brand new. just use the right oil CJ or the oil that's approved by Ford T6 is still not approved check out the video I posted about CK oil was shunned by Ford and why they turn their nose up to it certain CK oils not all of them take care

 

To the op. The 40 weight is the viscosity at running temp. It is a thicker oil then 5-30. The low number is the viscosity for low temp like below 40 degrees. so 5-40 or 15 -40 is a thicker oil then 15-30/5-30. So it provide have thicker covering on parts. the 30 weight oil does give you a tiny bit better mileage.





You can use dino 15-40 for towing. Right now I am using Motocraft 15-40 oil(Dino Syn mix). It is ford approved for heavy towing.