[Cwrose911]

I really depends upon where you live. I ran synthetic 15w40 in my truck until I reached 33,000 miles. The cold mornings (low 30s) made the starts rather rough. My last oil change I switched to Shell Rotella Syntehtic 5w40. The truck runs much better and starts alot faster with smoother idle. However, it rarely gets above the high 70s to low 80s here.

In the south, I would not run anything except 15w40.

I understand your train of thought but knowing the numbers…. The first number 5 or 15 is the cold viscosity… the second 40 is the hot. So a synthetic 5-40 doesn’t offer any less protection in a hot environment. Oh And the W stands for winter.

 

[bismic]

Good for the record, but this post is 15+ years old

 

[Charley#95]

I was thinking of using mobil devac 1 on my next oil change. what are the benifits/drawbacks of using a 5w-40 rather than a 15w-40?

thanks

2006 crew cb long box 4x4 with 13k

Hi dozer,
Make sure your oil meets the ford 171 specs, Mobil 1 and chevron do not meet the spec, due to them removing a lot of zinc in your oil. Try shell or if you can get it Kendall SHP And Phillips Guardall. Love those in my diesel.

 

[Big Horn]

Hi dozer,
Make sure your oil meets the ford 171 specs, Mobil 1 and chevron do not meet the spec, due to them removing a lot of zinc in your oil. Try shell or if you can get it Kendall SHP And Phillips Guardall. Love those in my diesel.

You’re replying to a 16 year old thread (2007) that somehow got revived. I’m sure he’s changed his oil by now 😉

 

[bismic]

lol - its no use. People just want to post something!