I had a 99 3/4 ton with the 454, loaded with a thousand pounds or so of work equipment it averaged 10-12 daily. My parents had it before i did for 5 years and my dad claimed it did an honest 12-13 on our trips to texas with justus in it and being easy.
My white 07 truck with 285's, 6.0 and 4.10 gears stayed at 10-12 mpg even with my most conservative driving and on a few non loaded trips. Towing my k5 that I had it sucked gas down but I also loved passing people and could easily do it loaded, had my friend Tj's burb that could not keep up with just its own weight to pull
People who claim they get 15mpg with a 6.0 are on crack. I have talked to several fleet customers and owners..they do not hit that number.
The one thing that is annoying with the 6.0 and the 4.10 gear and tire combo is it really liked to hunt gears a bunch and it was really annoying with my 40 series muffler. I had to go 5mph under it seemed to stay in the sweet spot, or 5-10 mph over. The only reason that sucked is because we had several trucks in our group and I didn't want to be that guy falling behind or taking off from everyone.
The 8.1 while affordable, is also not so affordable to repair. I am in the market for another 3/4 ton right now and thats the one thing seriously keeping me away from them. I have a customer that has several of them in his fleet and he has had almost half of them have the motors swapped out
The 6.0 will eat gas, the comment made above with 5,500 rpm is right on the money on a big hill and maintaining speed. You can get away from that by dropping down to second and lowering you're speed but what fun would that be
For me the difference between a 6.0 truck and a d-max is an easy 5-7-10k here. At 7k it would take a few years to make up the difference in gas. The 6.0 is also much easier to find parts for, quicker repairs and more versatility with what parts will swap or interchange " 4.8-5.3"
