Re: Surprising increase in truck MPG

I'd vote for the drivetrain getting broken in, with possibly an
adjustment for seasonal changes and/or fuel formulations.  I regularly
get 400+ miles from a tank of gas in my car in the summer, but it
drops to 325-350 in the winter.  I blame increased use of the A/C (for
defrost) and am curious if the difference between "summer gas" and
"winter gas" contributes in any way.

nate

Also in the summer your oil viscosity will be down. I'd suspect the
service 
station has been using a higher viscosity mineral oil. Don't think it's 
synthetic that makes the difference, I think its viscosity (at operating 
temperature). Synthetics hold their viscosity better as they warm up
(which 
goes the "wrong" way).