I fill the tank until I can see the diesel in the filler neck, drive it then divide the mileage driven by the gallons it took me to get the tank full again. I don't rely on the computer guessitmates.

Yes I checked that and my speedo is right on a couple of my friends have the gmc 2500 6.0 and can only get 13 out of them, another friend has a ford 6.0 diesel dually and he only gets around 11, while another one has a 7.3 SRW and he gets 17mpg and that we haven't used the computer to figure it just drive it sensible.

My '03 V-10, all stock, gets 11-13mpg non towing and drops to 7 when towing. When I get bummed about how bad my fuel economy is in the truck, I take the boat out.

DITTO......BZ

I have a 01 f250 v10 best Ive ever done was 18.7 aways easy on the take off don't hammer the peddle or they love to drink gas bad. have cold air inductive - hyper tec - dual exhaust . love the truck also if there getting bad g.p.m.try two things . 1st. disconnect battery for about 15mins than reconnect this will allow computer brain to reset . also try 91oct . but remember easy on the peddle its hard to but it pays off

That is very true if you're easy on them they are good a gas hammer at red lights and in traffic and they love gas

I have a '04 Excursion w/ V-10. Crossover exhaust tube was downsized at the "y" to a very restrictive diameter. Paid local muffler shop $80 to cut out & put in new Y same diameter as everything else. Noticable torque difference on hills.

Just ran from Mich to Fla over Thanksgiving. Overhead computer said 12.6 mpg avg. But if speedo read 75, my new Garmin GPS read 71, 80 on speedo was really 76 on GPS. I run stock 265 tires.

So might this also affect odometer and over (or Under?) estimate milage?

I've towed a 30' camper thru Rockies and my 35' Formula down to LOTO.