MPG and the OVERDRIVE button?!
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MPG and the OVERDRIVE button?!
Hey everybody. Been gone for awhile. Anyhoo . . .
Can anybody shed any light on a longtime household argument: "Is there any signifigant difference in gas mileage when driving in town (40 mph and under) with the overdrive on (light off) or overdrive off (light on)??!!
Can anybody shed any light on a longtime household argument: "Is there any signifigant difference in gas mileage when driving in town (40 mph and under) with the overdrive on (light off) or overdrive off (light on)??!!
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From: Nowhere, SE OK
if you are driving 40 mph and under, you shouldn't be in overdrive anyways. it shifts into overdrive around 45 mph in the vehicles i've drove in. out on the highway, you will be revving higher and getting less mpg with overdrive off.
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From: Sussex County, DE
Originally Posted by live2hunt
Hey everybody. Been gone for awhile. Anyhoo . . .
Can anybody shed any light on a longtime household argument: "Is there any signifigant difference in gas mileage when driving in town (40 mph and under) with the overdrive on (light off) or overdrive off (light on)??!!
Can anybody shed any light on a longtime household argument: "Is there any signifigant difference in gas mileage when driving in town (40 mph and under) with the overdrive on (light off) or overdrive off (light on)??!!
2) Your transmission will hunt and search more, causing increased heat buildup and increased wear. Unless you'll be engaged in steady state cruising at about 40-50 mph (depending on the gear ratio), you should not use Overdrive.
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Originally Posted by Argo
1) Your mileage can end up being worse around town,since you'll likely be lugging the engine sometimes, when you are on the bubble, so to speak.
2) Your transmission will hunt and search more, causing increased heat buildup and increased wear. Unless you'll be engaged in steady state cruising at about 40-50 mph (depending on the gear ratio), you should not use Overdrive.
2) Your transmission will hunt and search more, causing increased heat buildup and increased wear. Unless you'll be engaged in steady state cruising at about 40-50 mph (depending on the gear ratio), you should not use Overdrive.
Dono
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That's assuming that the engineer at the factory got it right. I've been questioning that assumption lately. Just go over to tccoa.com and look in the driveline section or the trans talk on their forums section to see how badly Ford missed on some of their early trans designs.
If the trans is shifting into od at 40 and that's the speed you're driving at then the engine will be running at a very low rpm. Add a slight hill to that and now either the engine starts to lug or the torq converter starts to slip. Anytime the tc is slipping heat is generated. Heat kills auto trannys. Also if you are driving right at the shift point and you hit a hill or other increased load, the tranny could be programmed to down shift. Hence the tranny shifting more often.
Around town I usually hit the od lockout button. I'm not going to be going fast enough to stay solidly in the od range (50+ mph) to make efficient use of it.
If the trans is shifting into od at 40 and that's the speed you're driving at then the engine will be running at a very low rpm. Add a slight hill to that and now either the engine starts to lug or the torq converter starts to slip. Anytime the tc is slipping heat is generated. Heat kills auto trannys. Also if you are driving right at the shift point and you hit a hill or other increased load, the tranny could be programmed to down shift. Hence the tranny shifting more often.
Around town I usually hit the od lockout button. I'm not going to be going fast enough to stay solidly in the od range (50+ mph) to make efficient use of it.
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From: California
Our powertrains are engineered to be used with access to all the transmission's gear ratios. I would estimate 1/10 of 1% of all driving is the type where you'd want overdrive off -- such as when towing in hilly country, or when you just want a little extra juice going up a hill on the highway. In my old Escape, there is one hill on a freeway near my house where I would oftentimes pop it out of OD, just to stay in the sweet part of the powerband. But I'm sure it cost me in MPG. Bottom line is, most people should not touch the "OD Off" button at all; it is there to use on rare, specific occasions. Keep the OD accessable for 99.99% of all driving if you want the best MPG.
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From: Sussex County, DE
Originally Posted by dono
I must disagree. (1) How do you "lug" an engine with a functioning auto transmission driving normally on city streets? (2) If your trans is "hunting" and "searching" or exceeding normal operating temperatures in normal city driving, it is not operating properly.
Dono
Dono
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From: Damascus-Boring, Ore
Are we talking older OD Automatics, or recent ones? Our '93 F150 "hunts" in the hills here at around 30-40 mph, so it works best with the OD locked out. Ditto earlier Suburbans we've owned. On the '03 Expy and the '05 Impala, the transmissions do a much better job of picking a gear, and there's no need to lock out of OD.
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From: Sussex County, DE
No,you are right there, with the later computer controlled autos on the hunting. But I still believe that low speed overdrive causes heat buildup due to being in a tall gear and slipping the converter, because you are not going fast enough to acheive torque converter lockup.
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From: Eastern WA
Originally Posted by polarbear
Are we talking older OD Automatics, or recent ones? Our '93 F150 "hunts" in the hills here at around 30-40 mph, so it works best with the OD locked out. Ditto earlier Suburbans we've owned. On the '03 Expy and the '05 Impala, the transmissions do a much better job of picking a gear, and there's no need to lock out of OD.
The earlier 90's ride I got is much different. Leave it in OD around town and it will engage/disengage the TC and 4th (OD) noticably. You can just sense this is hard on the tranny and of course I drop it into 3rd until my speed is over 45 or so.
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From: Sussex County, DE
I guess the main thing is to not allow it to hunt. However, like CowboyBilly9Mile said, "At about 40 MPH in 5th and with the TC locked the tach is at about 1750 rpm. If there is a "real" hill, it will first drop the locked TC, then if needed drop into 4th." This unlocking of the torque converter below stall speed causes alot of torque converter slippage and heat. I believe that (depending on the engine) the converter stall speed is between 2,200 to 2,500 RPM. I don't think that is healthy for the trans. However, I do admit that unlike the older automatics, there is a transmission fluid temperature sensor which is monitored by the PCM, and the PCM will adapt it's shifting and TCC strategies based on the temperature to protect the transmission from overheating I suppose. But definately pull it out of Overdrive if you notice hunting, or,if you experement and find that at lower speeds youget better mileage than with it in OD.
Last edited by Argo; Apr 12, 2005 at 08:01 PM.
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Originally Posted by Argo
No,you are right there, with the later computer controlled autos on the hunting. But I still believe that low speed overdrive causes heat buildup due to being in a tall gear and slipping the converter, because you are not going fast enough to acheive torque converter lockup.