Well I'm selling my 460 and just purchased a 2002 5.4. The gas mileage is great! See, it's all relative. If you are used to 12, then 16 is awesome. That's about what I get.
The 5.4 is plenty strong too, I think, and I had a torque monster 460. Are you pulling a trailer or just a loaded van? The 5.4 is plenty if the latter is the case, and I think 16 is average for these and not bad for such a large vehicle.
Good luck!
I'm gettin 12-15 mpg on my 2001 E250 (5.4L gas) with a high-top camper conversion. Not bad, my only complaint with the motor is the spark plug coils, they keep burning out. The coils aren't expensive, but they are difficult to reach making them a pain to replace.
I've got a 2011 Chevy 3500 Express EB. According to the computer after 8000 miles I'm averaging 14.7 overall. Other than one trip to Chicago we spend most of our time in North central New Mexico. We live in the Dallas area so we usually sprint out to Santa Fe at max highway speeds. Haven't had any trouble with climbing including Sandia peak in Albuquerque.
Linear Mode
