rooney77 wrote:
JAXFL wrote:
I have tried #5 and it stops some of the shifting
#5- You want to run Cruise - Push in the TOW button. You experience no downshifting even on overpasses. You get a very steady road speed. But it does not seem to do anything about increasing MPG.
I'd assume that would lower you're mpg. Basically tow mode just eliminates the OD (4th gear) so you're engine will be at a higher RPM at speed, same as if it downshifted.
On (some?) older Ford chassis, there's an overdrive off button on the end of the shift lever that does nothing more or less than disabling overdrive. That's what I have in my class C, with the venerable 4 speed transmission. (It's correctly labeled as "overdrive off", not as "tow/haul.")
On newer ones with the 5 speed transmission, the button is labeled tow/haul and has rather different effects. It doesn't entirely lock out overdrive, but it alters the shift point programming to (as I understand it) more aggressively downshift, less aggressively upshift, and to downshift automatically in response to braking when going down grades. I think it also adjusts some of the logic for when the torque converter is locked up with the goal of reducing transmission temperatures and such. This tow/haul mode is quite effective for heavy loads, much more so than a simplistic overdrive lockout.
Realistically, fiddling with transmission shift points isn't going to yield much better gas milage for a given speed and terrain. At least up to a point the engine is a little more efficient at lower RPMs, but the differences are comparatively small. Air resistance is proportional to something like the fourth power of speed, so slowing down a little results in a big savings. Air resistance at 72 mph is something like twice that at 60 mph. In other words, slowing down will have a much larger impact on gas milage than most any other easily made change, assuming the chassis is in proper repair.
