Drivetrain drag and variable mileage.

[BlueRu]

My '05 Baja Sport seems to have noticeable rolling resistance, but only when the engine is cold. Unfortunately, most of our driving is short trips around town, getting 12-15 mpg. On longer trips on the highway, I've gotten over 30 mpg. Why the drastic difference?

I've checked the rear calipers and parking (drum) brakes, but everything appears to be in order. Could this be a matter of old differential oil causing drag until it warms up? Do you think I'd see a difference replacing the diff lube, maybe with synthetic?

Has anyone else experienced this?


Thanks,

R