ssiredfish
Senior Member
I always keep the overdrive off when trailering around town but is it necessary to keep it off when you are on the interstate maintaning a constant speed? Trying to get better than 8.3MPG on the interstate

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Look at the computer and see what the mpg is when in OD and not.
In my situation I found I get the same or better mpg by turning the OD off.
Yea 3mpg difference....doesnt sound like alot but thats a 30% increase for me.
MJ - I was ALWAYS told the same.....thats why I had to ask
I have a 2005 Chevy 2500HD and the boat with my gear comes in right under 4000#(truck excluded)........I also hate that when OD is on with cruise control and I hit an overpass, the SOB acts like it wants to redline to get up it and just guzzles gas.....
I will try w/o the OD on this next trip and see how it goes. At 1200mi roundtrip I need all the help I can get!!! Especially when my normal fuel econ with no load is 11.3mpg!!!! Ol girl is tough but she aint a cheap date by any means......
Put it in tow/haul mode and go with it. No need to shut OD off for that. Heck I've towed ALOT more than that with a 6.0L 3500 SRW, and it towed just fine and stayed in OD. As for revving up, the VORTEC engines do NOT like to be lugged down. They run the best high up in the RPM's, and it is probably helping your mileage in doing so(and also helps your trans).
I thought that tow/haul mode took it out of OD???? Am I mistaken?
Kevin - I shudder to think of what my MPG would do with that load!!!! Id have to pick up a night job just to afford to move it.....
2001 Ford F150 Crew Cab w/5.4 litre 2wd...tow my v20 from SC to FL, NC, TN and anywhere else Ive ever taken the boat WITH OD on...no problem...
Seems to me a 2500 HD should tow a V20 in OD w/no sweat at all...the only problem I see in yer posts is when ya got Cruise Control on...that's something I would NOT expect to work well and wouldn't do w/my truck...
pretty much the only thing that will help that is slowing down.... I had a suburban back in the day with 3.73 gears and 38" ground hawgs... it got about 11 mpg.... The auto O/D trans went bad on me and I drove it to work and back for a few weeks with only 1st and second... I drove it at 55 mph in 2nd gear and got 11 mpg ..... didn't matter if it was running 4000 rpm or 1600 rpm... same mileage