Another consideration would be dragging brakes.If a wheel is not fully released after braking it's like dragging your foot on the ground. Following a run, check for heat on the drums, or jack up each wheel, apply the brakes, release, and immediatly determine wether the wheel revolves easily. My motorhome vexed me for the longest time (6-8mpg) until a quick stop on a greasy road revealed left rear wheel drag. Fixed that and have 10-11mpg. It's like life - the little overlooked things drag you down. :o)
Laurence
