Chat with a diesel mechanic buddy changed how I see oil weights

I was helping my friend swap out the oil on his '97 F-250 last week, and he got into this whole thing about how modern 5W-30 is actually way better than what people used to run in older engines. He said the tighter clearances in newer blocks just don't need that thick 15W-40 stuff anymore, even in summer. It hit different because he's been rebuilding engines for like 15 years and isn't just repeating internet gossip. Has anyone else switched to a lighter weight and seen a difference in cold starts or mpg?

2 comments

2 Comments

tessa_kim34d ago

Did you notice any actual difference in mpg after switching? I read a thread on a different forum where a guy tracked his fuel economy over six months and said he got about 2 miles per gallon more with 5W-30 compared to 10W-40 in his old Chevy. He was pretty convinced it was the lower viscosity helping the engine not work as hard.

jordanc683d ago

@tessa_kim3 +2 mpg sounds about right, less drag on those cold starts for sure.