I'm wondering. My '05 Escape has overdrive that I can turn on or off at the touch of a button (V6). I've noticed it shifts in and out a lot when driving around town (I can't feel it, but I can see it on the tach). Do you think my mileage would be better if I turned it off around town? The default when you start the car is ON.
The salesman told me was when driving up and down hills and when it's really curvy turning the OD off does help with engine braking and has more control, and it does.
Are you sure it's shifting in and out of OD rather then locking and unlocking the Torque converter? In my experience I can almost always feel an OD shift but lots of times I can't feel the TC lock/unlock even though I can see it on the tach.
I believe Ashton has hit it on the head. My '02 Escape is like that; at times, I can definitely feel it shifting, but for the most part, at in-town speeds, it's the TC locking and unlocking. Generally speeding up or slowing down a couple of MPH stops that. Either way, I don't think your mileage is affected enough to worry about it.
No, shifting takes hardly any fuel. And, when it is in overdrive, it is using as little fuel as possible. Keeping in OD will save some fuel and not hurt your truck at all. Except when hilly, leave it in OD.
Don't know about the F150, but SOME vehicles DO get better fuel under some conditions with overdrive disabled. Cars with variable valve timing will generally NOT, because they are "on the cam" from basically idle to full speed - while vehicles with fixed valve timing can be "lugged" which hurts the fuel economy.
I KNOW that my PT Cruiser does do better mileage wise if Ikeep it out of OD in some conditions -with the vehicle loaded. Lightly loaded, no.
The tranny seems to make the transition very smoothly, but the tach does jump up or down about 500 rpm. If I turn off the OD the tranny feels just as smooth, but I don't see the tach jump up and down. The car also has better throttle response both on and off.
Thanks all. I thought about doing some experiments to determine if it does get better mileage one way or the other, but I would have to drive the exact same course over and over which would just be a waste of time and gas. I don't have a normal daily commute. I do live in the mountains, and it's easy to "feel" that when driving in curvy hilly places the response is much better with OD off. Since it's an automatic I don't really have the control I would have with a manual and a switched OD.
The car drives very smoothly but the tach does dance around a lot with the OD on. You can't feel it, but you can "see" it.
On Tue, 12 Apr 2011 19:54:07 -0600, "Sheldon" wrote:
It's just my $.02 but, in the Ford and most others I have seen, leaving the trans in the default OD position and letting the PCM make the shifting decisions is usually the best. Different vehicles have different programming strategy but, OD is a fuel economy strategy whereas disabling the OD not only kills the OD but, changes the shift strategy to more of a performance strategy which may or may not affect fuel economy favorably. In the default mode, the trans will normally unlock the torque converter for a few extra RPM's and a slight increase in power. If the load remains too high for the OD gear ratio, the PCM will drop it down a gear or two as required to meet the power demand. By disabling OD, you lose it's ability to take advantage of the drive ratio with the converter unlocked for whatever fuel saving could be saved with that strategy alone and guarantee there are no savings from the OD. Unless you are in a situation where the trans is hunting between OD other "gears" it is usually best to just let it do it's job. The manufacturers have done much experimentation in this area in search of maximum fuel economy ratings and production. One thing you should do with your indicated driving conditions where the trans frequently shifts is make sure the trans is regularly serviced. An add-on fluid cooler - in addition to the factory cooler - to make sure it does not get ony warmer than necessary can greatly increase transmission life. The best thing to do with the OD is sit back and enjoy the ride unless it starts hunting.
little OT, but is it even a good time to have an F150 IN O/D when towing? Maybe just flat level highway? Or will it be hunting around popping in and out too much? Just curious as I'm planning to haul a 6K lbs camper around...
You have the same control - mine is an automatic too. On mine I have a 1,3, and D position on the shifter. The D is in a circle - meaning OverDrive. Driving in 3 keaps the 4 speed automatic from shifting into OverDrive (4th).
On my wife's Mystique it has 1,2, and D, plus a green Overdrive button
- On the Ford I can shidt manually 1-2-3 then turn on OD. On the PT, to do the same requires starting in 1, bumping the shifter to 3 then pulling back to 1 for second, bumping to 3 for Drive, and then to D for Overdrive.
Not true in MOST cases. MOST automatics do not have variable shift strategy - and those that do have (generally) a "mode" button.
And it will start hunting a lot sooner with a load of any sort than empty. 4 passengers, without luggage, can make the average vehicle "hunt" a lot below about 110kph. The "fuel economy" programming the manufacturer has "optimized" for is the test cycle - which does NOT account for a load.
Nobody wants to believe me, but I posted the figures on a different newsgroup 2 years ago - with 4 adults and luggage in the PT, in OD, at 100kph, from Waterloo to Montreal it got under 20mpg.
From Montral to Quebec city, same load, still in OD,at 110kph+ I squeazed close to 25mpg out of it (Canadian Gallon), and from Quebec City to Fredericton, same load, shifting out of overdrive, and manually downshifting (much earlier than automatic wanted to, keeping RPMs up), through the hills, and averaging closer to 115kph, I averaged just under 34MPG (Canadian).
It defies accepted common knowlege, but my explanation is I allowed the engine to "breath" -keeping manifold pressure high (relatively low load) and running in the more efficient range of RPM.
The 2002 PT cruiser develops Max torque at 4000 RPM and max power at
5100 RPM. Overdrive cruise at 100kph is about 2200 RPM.
At Max torque RPM the car would be doing 116MPH, where the CD of something like .42 would definitely cause a significant hit to gas mileage, but allowing the engine to pull higher revs under less load when it is working, and then allowing it to shift into overdrive and basically coast down hills was an effective strategy for fuel mileage.
I would NOT run it in OD with a 6000 lb camper - you need the engine revs to give you the required power without demanding high torque (low vacuum, rich mix, retarded timing, etc) and you also want the engine braking capability that OD does not provide, for maximum combined vehicle control..
Understood...By default it's on. Just have to remember to push the button on the end on the F150's shift stalk after hooking/and starting up each time...Then again, I'm sure it won't take much for the truck to gently "remind" me I forgot once I got up to speed, other than a mechanical hand extending from the dash and smacking me in the head. :)
And it is programmed that way by the factory to meet the emissions and fuel economy requirements dictated by the government - where the tests are done with unloaded vehicles. - and you cannot change it.
The programming CAN be changed. There are numerous devices on the market that allow you to do so, and programs associated with them for different situations such as lower or higher octane fuel, better mileage, more power, different shifting schemes, etc.
Programmers are available for diesel engines, and for V-8 engines. I have found none for 6 cyl., and V-6, engines. Wife bought an S-10 with a 4 cylinder engine, all I found for it was a chip.... It made minimal power increase. I bought the chip for $24.95, but doing further research I found out I could have bought resistor from Radio Shack and done the same thing for $1.00
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