Better mpg at higher altitudes?

[Cubey]

Maybe it’s my imagination but it seems like my mpg got better once I got above 5000ft. Maybe it was just tail winds or being easier on the throttle but it seems I jumped from 13-14 hwy at 65-70 to 15-16.

I lost 1.5mpg after I replaced my worn out put highway tires with cheap all terrains so 14-14.5 is about what it “should” get. I got 15-16 before.

I went from about 12 city to about 10, near sea level.

Or maybe diesel is better quality in Wyoming? Hmm.

 

[Thewespaul]

Hmmm wild guess but I’d say less fuel pressure which retarded your timing a bit and the engine liked the change