we used chevy one ton vans since 1989 -- replacing them every five years. now we carry a full load all the time! we always had the 350 gasoline engine and the average true milage was right at 8 mpg! we would service the vans every 3000 miles and seldom had problems and got about 150,000 miles in their five year stint with us.. then, one year i was shopping for a new van and the salesman made me an offer on a 2000 diesel with extended body--one ton-- for 22k! this was cheaper than the other dealers with the 350 gasoline engine. i bought the diesel. it also had the all the bins in it set up for our trade! my milage doubled!! 16 mpg loaded or unloaded!! and more power. i found out later the salesman made a 3k mistake -- it was supposed to go for 25k.. i am sold on diesels and have since went diesel in my pickup trucks --- dodge 3500 ---2003 ---168,000 miles--no problems--22 mpg -- basic cost difference is about 5k and you have your money back inside three years--better resale also. i look at the cost of diesel fuel(which i believe to be pure BS) that i get twice the distance per gallon of that of gasoline. and with the increased cost of fuel that payback is alot less today... warmup should not be much difference than gasoline engines -- did they leave the thermostat out??? i've got warm air coming out of my vents within two blocks of my driveway!!!