While in the Army, I drove a duce-and-half that had a valve stick. We fell behind the convoy with a top speed of 25mph. 1st Sarge said to sneak about a quart of diesel in the tank at night. Not sure, but I suppose I might have maybe put in a gallon. Next day that truck out ran the convoy. 1st Sarge was right, it did free up the valves, of course, 2 weeks later the engine blew up. That was my last time driving Army trucks, darn the luck!