5w40 in 03 Yukon XL Denali?

[DROCK84]

I just purchased an 03 Yukon XL Denali, brought it to my mechanic to change all the fluids when he recommended I return the Mobil1 5w30 Full Synthetic High Mileage I just purchased and buy 5w40 Synthetic instead. I'm confused, why would I change to a German Gas/Diesel oil instead of the normal 5w30??

Has anyone had any problems using 5w40 or has anyone heard of this before?

Thanks

 

[mizzouguy]

I've heard of people switching to 10W-40 conventional if their engine is pretty worn and leaking/burning oil. Or even 15W-40. And I know they make 10W-40 in synthetic although not many places carry it. So not sure why he would say 5W-40....like you said european/diesel...I think you would be better off sticking with 5W-30 or 10W-30.

 

[TommyR]

I run 10w-40 in mine with no issues. I have lower oil pressure when its cold due to how thick it is, but thats it. My mechanic recommended it due to oil dripping through the valves. If I was idling for a minute or more I would blow blue smoke everywhere. Fixed the problem about 90%.

 

[PG01]

Shit, I remember when all we used was 10w40

 

[SirReal63]

I run 10w40 in my 03 2500HD, have for years. It is also at 314k miles, I started doing it before the oil pump was changed, and it did help to quieten it down.

 

[Rocket Man]

Umm...did you ask your mechanic why he suggested that?

 

[RST Dana]

We used to run Kendall 50W in all of our toys. This was before synthetic was born.

 

[DROCK84]

Umm...did you ask your mechanic why he suggested that?

I did, he told me because I have 217k on it that if I put in 5w30 synthetic I might get oil leaks from worn out gaskets or rings. He "required" 5w40 synthetic as a way to help fight that issue and says he puts it in all the cars he works on that call for 5w30. Also, I believe he wanted to use the 5w instead of 10w due to how cold the weather gets around here.