Originally Posted by 99Smokin73Stroker
23, wow......you drafting tractor trailers?
I see all kinds of 6.0 mileage in the high teens to right around 20, but I have seen few claim to get into the low 20's too much. It's just like any engine though, same engine but fuel mileage can be low, normal and high.
Absolutely agree!! I have spent years on multiple forums reading up on the 6.0L and fuel economy. On highway driving w/ a tail wind, you may get 20 to 21 unloaded. I am averaging 17 now, w/ very little stop&go / short trip driving. Best I have done is 21 - again w/ a good tail wind. I use fuel additives, keep filters changed, keep EGR valve clean, have the most recent flash update on the control programs, etc. I also have done a few mods like the power elbow that have been claimed to help mpg (if they do, it is few tenths - which I will gladlly take!). Tire size makes a difference. I have 20's, but would recommend 17's.
Be sure to ONLY pay attention to hand calculated results - the electronic readings can be way off.
One thing I have not researched - the difference between manual and auto transmissions and how much better fuel economy is w/ the manual. Some of the 20+ mpg results may be w/ manual tranny's.
Some folks w/ tuners have claimed in the 23 range, but very few! I have never seen a spreadsheet or graph from someone who claims 20+ for anything more than a rare occasion.
Solid trucks should average around 16 mpg w/ 18-20 on the highway.
The 2005 is a good truck but they have a history of problems w/ the HPOP (high pressure oil pump) STC (snap to connect) fitting. Find a truck and then get the VIN number so you can get an OASIS report (this is the Ford repair history from their database). Also look for flash upgrades after 4th Qtr 2007. If you are buying from a dealership - negotiate for a new EGR valve, HPOP STC bracket installation, and the newest flash.