10-30 or 5-40 for MPG's?

[wtd]

My Girlfriend has a 2003 F350 superduty 4x4 with the 6.0 diesel and has used 10w30 Motorcraft diesel oil since new and does 5,000 mile OCI's. The truck has almost 68,000 miles on it with no engine problems. This is the viscosity the dealer's around here recommended. She doesn't tow much with it but we did take a 2,500 mile cross country trip last year in July pulling my 18' flatbed carhauler with a car on it for the last half of the trip and the engine never used a drop of oil.

She buys the oil at the dealer and I change it. Its only a little over $2.00 a quart.

Wayne

 

[rg200amp]

68,000 miles on a Diesel?!?!? That thing is still breaking in!!!!!

 

[Toy4x4runner]

good to know. thanks.

 

[bmwtechguy]

I would use Schaeffers 15w40. Excellent fuel economy and engine protection. My BIL uses it in Pensacola FL year round and is very happy with the perfomance in his 6.0 He has been going 12-15k miles oci on this oil with zero consumption and good viscosity retention. He tows some heavy stuff around several months of the year, too.