buddy of mine has a 08 1500 with the 5.7 and he said that his mpg is 7 on his truck where as my 07 1500 5.7 is getting around 14 and 11.5 towing
he said he replaced the battery in the truck and it went back up around 14 or 15 then slowly went back down to 7. he said he's tried different fuel grades (87,89,91) and all are pretty much the same to little or no difference
its got me puzzled as to why it would be so low
hes got a leveling kit and i believe 33s ( still wouldn't think it would be that big of a difference)
any one have any ideas? thought maybe a tune up but idk why when he changed the battery the mpg went back up then back down
-thanks!

 

Does he idle his truck a lot? When I had my truck I would idle it for like 20 minutes every morning before high school, and I began to average like 9 MPG.