Whats the difference between driving with O/D(overdrive) on and O/D(overdrive) off?
Which is more fuel efficient?
I see the button I can use to turn O/D off but never bothered to know what id does except that it shift gear at a different RPM
2007-01-04 18:29:03 · 5 answers · asked by zoomzoom 2 in Cars & Transportation ➔ Other - Cars & Transportation
The overdrive button was mainly designed to prevent the car from dropping into it's highest gear ratio when towing or ascending hills, thus allowing uninterrupted pulling power.
Most modern automatic cars these days do without this feature as the computer can detect and adapt the gearshifting to your driving style.
For example:
I drive a relatively late model 4 speed automatic which has what's called an 'adapative' automatic transmission.
What this means is that it will learn my driving style and adjust the gear changes to suit. If I am driving sedately, it will slur through to the next gear and change at much lower rpm. However, if I am doing some spirited driving, the auto will adapt by holding onto the gears until higher rpm and make quicker gear changes.
Or perhaps say I was driving up a long and windy hill. In a car with the O/D feature turned on, the automatic is likely to 'hunt' between say 3rd and 4th gear as the road gradient, speed and your pressure on the gas pedal, amongst other things, change. In this scenario, the automatic cannot decide which is the best gear to be in because of these changes. So it just keeps hunting until you reach the flat when it changes and stays in 4th. Can you imagine how annoying, stressful and the impact on fuel economy this would have if towing a heavy caravan?
However, with an adaptive automatic, it can sense that you are driving up a long and windy hill through your driving style and hold 3rd gear the entire time, even if I momentarily release the gas, thus avoiding the hunting, providing acceleration uninterrupted with repeated gear changes and saving fuel. Turning O/D off in this situation allows you to do precisely the same thing with the press of a button.
2007-01-04 21:56:54 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Generally you want the overdrive on. Over drive is the highest gear and is used to get good highway mileage. The more RPM (revolutions per minute) that your engine is makeing the more fuel it is burning. However engines dont make much power nor are they efficient at low RPM,s. This is why they have the button. In hills or when towing, you may not want the car to shift into Overdrive. The car may need the power to pull the trailer or go through the mountains. In 99% of driving conditions leave overdrive on, modern automatic transmitions will shift when they need to. So dont limit it.
2007-01-05 03:08:02 · answer #2 · answered by theascheick 1 · 1⤊ 0⤋
The OD gear is for fuel efficiency. You can turn it off if you're towing something or its too sluggish at higher speeds for your liking
2007-01-05 03:24:31 · answer #3 · answered by SargentNG 2 · 0⤊ 1⤋
I had on in my Geo Prizm, and I kept it shut off if I was in the city going no faster than 40 MPH. I didn't like the fact that it kept shifting in and out of OD constantly at lower speeds. IMO, that just creates unnecessary wear.
2007-01-05 03:34:41 · answer #4 · answered by Anonymous · 0⤊ 1⤋
the difference is simple the first one is in on possition and the second one is off
2007-01-05 03:10:51 · answer #5 · answered by Sonu G 5 · 0⤊ 1⤋