Dont know what to make of this. Maybe nothing. In route to Yuma Ariz. this Feb. my tach. was showing between 2,000& 2,250 rpm, this running between 60&65 mph. towing a 27 ft. 5th. wheel. I normally run from 1,750 to 2,000. Stopped for fuel and short rest. When back on road tach. was back to normal 1750 to 2000. Same conditions,same wind. Did this once more on way home. Any thoughts ? Just tach acting up?This on my 93 D250. Thanks : Bob