subprime

been driving my 95 3.0 slow and the car is more comfortable with the O/D on.

Does it waste more gas on or off?

I feel more power with OD on. When coasting on the freeway my rpm is about 2900 going 70mph. With the OD off, I'm at 3900 - 4100 rpm when going 70mph.

Elton

leave it on its like haveing a extra gear wich means better gas mileage

95RunnerSR5

i dont understand how people think havnig overdrive off saves gas....when your rpm's are higher with it off you have to be burning more gas...a few friends of mine are convinced it doesnt burn more gas but i just tell them its their money

Chuki

If you have a load or climbing some hills, its best to turn it off, otherwise you'll be in and out of O/D alot and thats not good, but if your crusin the freeways with no load, turn it on and save a little on gas. You'll save a little, but not much. Just depends on the conditions. Sometimes with O/D off you can save gas cause you don't have to give it as much pedal to keep your speed, vs if you do have O/D on.

regularguy412

I seem to get a little better economy in around-town driving by leaving the O/D Off. My 3.0 seems to be most efficient around 2,800 RPMs. I agree with chuki. I'm not sure that dropping in and out of O/D is such a good thing for the tranny.

Mike in AR

curtiswyant

OD is for the highway. It's like 5th gear in a 5-speed. You don't need it around town.

AH64ID

I keep OD off in vehicles I drive if I am below 45. At slow speeds and low RPM;s, like OD at 30mph... I do not feel that there is enough cooling, therefore the trans runs hot. Also lots of shifting produces heat...

You will get the best MPG with whatever gear puts the engine in its deisgned RPM range, 4cyl higer than 6, which is higher than 8cyls.... See what your engine likes best...but for longer tranny life keep OD off below 45ish...

midiwall

because of things like...
It's a matter of efficiency.

If you were on an infinite road that was perfectly level (or otherwise be able to provide a consistent load to the engine) then choosing a gearing that would _maintain_ a given speed at minimum engine RPMs would provide you awesome fuel economy. But, the minute that you needed to adjust the engine speed due to a change in load (a slight incline, a turn, resuming from someone slowing down in front of you, etc.) you would pay the price for the higher gearing.

The engine would bog down due to lack of available toruqe, which will cause the ECU to start pumping in fuel, the RPMs would climb up, the vacuum in the TB would increase, the vacuum sensor for the tranny would kick in and downshift, the RPMs would climb up fast, you would panic and take your foot off the gas, the tranny would upshift, the engine would bog, you would swear and floor it, the tranny would downshift TWO gears, the RPMs sky rocket....

...and you just wasted more fuel than idling in your driveway for 10 minutes.


It's mentioned in another thread around here, but drivetrain designers chose the ratio of the overdrive gear for a balance of power, efficiency and noise level. The scale is weighted, but one thing that's at the bottom of it is _driveability_.

So, depending on the type of driving you do and the terrain you do it on, you may get better mileage by NOT being in overdrive.

AH64ID

subprime

so if im in city streets, with lots of starts and stops and changing lanes, and slowing down for turns, I should have O/D off.

if im on an empty freeway needing to travel 300 miles with no other cars on the road, no hills, just flat roads, I will be more efficient having the O/D off?

If this is true, what about someone else's comment stating that it is bad for the tranny to keep switching the O/D on and off. is this true?

midiwall

Yeup.


That may be a brain fart on your part , but in this case you want O/D _ON_.


They're talking about the tranny dropping in and out of O/D on it's own which is just unnecessary wear & tear.

For example, when I'm headed up a long 10% grade on the highway, my tranny will tend to bounce out of O/D, then back in, then out, then in... That's wear & tear. If I pop it out of O/D, then it'll stay put in 3rd ("Drive"). Once I'm at the top of the grade, I'll put it back in O/D.

95RunnerSR5

sorry i didnt think about that...i live in hurricane ravaged south mississippi where there are no major hills to speak of so overdrive is always on

regularguy412

Also -- don't get confused with the O/D kicking in (when you have it 'on') and the locking of the torque converter. It's 'supposed' to lock and unlock as driving conditions, engine load and throttle position. If the converter didn't unlock when you take your foot off the gas and slowed to a stop,, the engine would die.

Mike in AR

YotaND

I think it does NOT matter if your OD is on of off durring city driving. My understanding is that OD will only kick in when you would normally use 5th gear with a manual. Think high speeds. I never get my truck in 5th geat when I'm driving arround town so my manual in my runner shoulden't see 5th either.

I think OD should always stay on unless your are towing or placed in another situation where gears might change often (in ND the winds alone make me drop out of OD all the time.)

midiwall

Could be different on your rig, but I know that my OD kicks in just about any/all the time that I'm not accelerating.

Try this on your (or anyone else reading) auto the next time you're cruising the local Ben & Jerry's on a Friday night. Hold a steady speed (say 30mph), and hit the OD button. The light should come on and I'd bet that your RPMs go up. The latter will be a sure inidicator that you just dropped down a gear.

AH64ID

In every auto vehicle I have driven, they upshift at the earliest possible time, My 03 runner will go into OD at 25-30mph. they will also upshift into OD if you let off the gas at slower speeds. It then downshifts as soon as you give it more gas, think how SLOW your tranny is cooling at those speeds...

Now there is more argument with you... In the last few years cars have stopped saying D and O/D, they say D,3,2,L, or 4,3,2,L....but I still wont use OD/4/5 in city style driving, or cruising below 45... 1400 rpms isnt enough for me...

trythis

Its an automatic transmission for a reason: It's Automatic!
If your engine is gear hunting going up a hill, or when towing a load, you turn OD off, it that simple. You can even look it up in your owners manual, or ask the car talk guys.

AH64ID

You drive your auto how you want, my money is on mine lasting longer...

Owners mauals are build for people that hardly know that the engine is in the front of the car... And it serves them just fine...

My dad got 2times the normal life out of his suburban with a 700R4 becuase he drove like we are explaining here...not coincidence....

regularguy412

If I turn it on, my O/D will kick in (after the necessary warm-up) anytime my groundspeed is at or above about 40 mph ( and not accelerating). That puts the RPMs down at a miserable 1800. In my opinion, that's far too low for good fuel economy since the engine is really dogging around. I really feel like the 3.0 is much more at home around 2800 RPMs.

Mike in AR

trythis

SO how about using the ECT POWER button in town as opposed to OD off. In town for me means speeds above 45 and popping on and off highways. Not hours of trudging through a Manhattan style gridlock. No thanks!

<Just teasing> You mean he got 120,000 out of his GM tranny instead of 60,000? </Just teasing>
I had a GMC automatic and it was fine, in fact it had a tow/haul mode that seems to operate similar to the ECT power button in my yota. The GMC was much newer so the tranny (when that button was pressed) actually adjusted for the weight and load that was actually put on the tranny. That way it could go into OD even with a heavy load, if it wouldnt hurt anything like when it was going down a very slight hill. The diesel version of my GMC had a setup that would even downshift automatically on steeep inclines when the cruise was on.