10 is horrible. you definitely got something wrong.
however be aware a 3.9 is grossly underpowered for moving that much load. I had a dakota with 3.9 and one with a 5.2 and the fuel mileage was nearly identical. then I had a 2.5 4cyl stick minivan and a 3.3 auto grand caravan. the 4cyl van was only 2mpg better than the 3.3. so a smaller engine doesn't = better fuel mileage. but 10 is really low unless you live in high traffic or very hilly geography


I have a 1997 B3500 maxivan w/360 and it has 310,000 miles. I tow a race car with it and average 12mpg towing, 15 empty.

I also have a 1990 dodge roadtrek 318, 80,000 miles. in June, I drove to Portland, down to San Luis Opispo back to the midwest 6000 miles round trip. my average fuel mileage in total was 15.2. I had as high as 16.8 lowest was 13 in the mountains


side note: why is the word V I R T U A L a blocked word on here????? I typed it in and what it converts to ******* ????? *******

 

Changing your oil will help. The dealer we bought ours from only put 4 quarts instead of five, giving us 12/16 mpg instead of 16/24 after I changed the oil.

 

I have a 2001 3.8 liter, we used to get appx 20 MPG, now it has dropped to Appx 16-17 depending on gas, I did tune-up, tire pressure, gas filter,etc. basic stuff. I do smell slight gas fumes when I start the Van, engine light is not on, could it be a problem with the oxygen mixture or something similar ?

Thanks for anyhelp

Rich