GMC 6.6 Oil Change

[Rogerb3116]

My son just had the oil changed in his 2021 GMC 2500 with the 6.6 diesel at the GM dealer ship. They put in part no. 88865796 15w40 and told him it was synthetic oil. I have never heard of a 15w40 syn. I think they scammed him. Any thoughts?

 

[Rat407]

Just your basic AC Delco synthetic oil from what I understand. Nothing special.

 

[Dave Hess]

My son just had the oil changed in his 2021 GMC 2500 with the 6.6 diesel at the GM dealer ship. They put in part no. 88865796 15w40 and told him it was synthetic oil. I have never heard of a 15w40 syn. I think they scammed him. Any thoughts?

Syn 15w40 oil has been around for a long time.

 

[UNC054]

If it’s AC Delco it might be rebranded Mobil

 

[4wd]

If it’s AC Delco it might be rebranded Mobil

View attachment 88610

Yeah - and FF is Delvac semi …
Some GM dealerships that had two free oil changes would let you upgrade for a moderate price …
Either can run to the Owners Manual limit …