Fuel mileage
one of my customers is running a combo of motors in f450's the 6.4 diesel gives him 7.8 all the time .his v10 runs in the low 12 unloaded and 10 loaded.it all depends onyour right foot.
just with the 6.4 ! you can not control the amount of the wasted fuel when it cleans the carbon canister every so many miles. that is no matter how lite your right foot is. another factor is the almost 10k cost of the 6.4 over the 600 bucks for the v10 and price difference of gas ver diesel right now. both motors are built for working with a load in or behind them.
I get 13 driving back and forth to work, 16 out on the open intersate cruising at ~65 and 7-10 towing (7 for clibming and 10 on the flats) pulling my 9k TT.
@8/8.5 on tpks and interstates at 63/65 MPH. In mountains, long step grades we would drop to as low as 4/5 mpg. at altitudes of over @6K we noted a loss of all over power but the V-10 did the job, we had no complaints. Not towing and careful driving we got a all over average of @ 10/12MPG on tpks/interstates..saw as high as 14 in flat and windless S.D. We now have a 08 6.4L..(we just do thats all). The increase in MPG is not all that much 2/3 towing/3/4 solo.You would need to drive a long time to break even on the cost of the 6.4L. Top That.you should be doing beter than that on your 6.4L check your tail pipe for black soot for starters and if you are runing 75/80MPh and high boost that will be about as good as you get.



