I was doing some digging for ISX for Drag formulas and such and ran across this page and had to share with you... http://ecomodder.com/forum/tool-aero-rolling-resistance.php#2 Here is what I figured out for my Empty run and my 235/85 R16 tires (Crr .009) http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=7900&WeightUnits=lbs&CRR=.009&Cd=.45&FrontalArea=37&FrontalAreaUnits=ft^2&FuelWh=37953&IceEfficiency=.22&DrivetrainEfficiency=.95&ParasiticOverhead=0ρ=1.164&FromToStep=40-65-1 Then here is my offroad 265/75 R16 tires (Crr of .015) http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=7900&WeightUnits=lbs&CRR=.015&Cd=.45&FrontalArea=37&FrontalAreaUnits=ft^2&FuelWh=37953&IceEfficiency=.22&DrivetrainEfficiency=.95&ParasiticOverhead=0ρ=1.164&FromToStep=40-65-1 Then my truck full loaded with 2 cords of firewood and trailer... http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=13500&WeightUnits=lbs&CRR=.015&Cd=.45&FrontalArea=49&FrontalAreaUnits=ft^2&FuelWh=37953&IceEfficiency=.22&DrivetrainEfficiency=.95&ParasiticOverhead=0ρ=1.164&FromToStep=40-65-1 Then if I just change back to my street tires... http://ecomodder.com/forum/tool-aero-rolling-resistance.php?Weight=13500&WeightUnits=lbs&CRR=.009&Cd=.45&FrontalArea=49&FrontalAreaUnits=ft^2&FuelWh=37953&IceEfficiency=.22&DrivetrainEfficiency=.95&ParasiticOverhead=0ρ=1.164&FromToStep=40-65-1 It goes to show the effect of speed, tire, frontal area, etc all have a huge effect on MPG!

I want to make a spreadsheet of all that too, but factor in RPM. IMHO, I think 1500-1600RPM is most efficient, equating to 50-55mph. This is speaking in a real world sense. 1300-1400RPM might be better, but you get to any hill and now you are lugging it and the turbo is well below spool speed and you can watch your fuel shoot out the exhaust. With that in mind, the only way to really factor it is to get some solid data on just how much more fuel it takes to do 50mph in 4th gear than in 5th. In theory it would be the same, but having to turn the engine more RPM does cost something. Just wondering how to figure it.

Thats some cool info, but I wonder how much modern emissions effects that?

Pretty cool info. but too much hassle. Reminds me of my past days filling out PPC cards prior to flight on a checkride.

PPC cards

Performance Planning Card cards? Yeah, the one a year long hand sucks! Thank god for the PPC program! I had to do one a day at the MTP course this spring, by hand.. I honestly think that was the most annoying part of the course..