What are the uses of overdrive and when should it be used?

Using Overdrive

Here are opinions and answers from FAQ Farmers:

• (BEST ANSWER) In simple terms, overdrive is like a fourth gear. When you turn it off, then there are only 3. There are some situations (like towing or going up a gradual incline) that the car should automatically downshift but it does not. For normal driving, it is recommended that you leave the transmission in over-drive mode. This will result in the best fuel economy. It is also worth noting that when the vehicle is started, the overdrive is turned on automatically.

(The rest of these entries are of dubious merit.)

• Overdrive gives a little better mileage on the open highway. Stay in Drive for stop and go traffic or speeds under 35 MPH.

• I asked the dealer this when I first bought a Mitsu PU. It was auto w/ overdrive. They said to leave it on all the time. Well, thanks to that brilliant advise, my trans went out at 60k. Luckily, I had a bumper to bumper warranty and they had to drop in a new trans for free. Now I know. Don't push that button unless you are at highway speed. City driving requires leaving overdrive OFF! This trans has gone 200k with no problems. Good luck!

• Over drive essentially adds an extra gear to your drive ratio effectively lengthening your final drive ratio and causing your engine to maintain lower RPMs. It should be used on the freeway. It conserves fuel during long drives at a steady speed.

• If towing or in high snow leave in drive as leaving in od can cause tranny failure due to intermittent on off load shifting. Was cause of my GMC tranny failure as i left in od when hauling loaded trailer in hilly terrain.

• During general driving it is fine and better to leave it on, even while city driving. The times to turn it off: 1)when you are towing something, or may have a heavy load or 2)when you are driving in the mountains; while going uphill sometimes O.D. will shift back and forth frequently, if this occurs definitely turn off the O.D. so the tranny will not over-heat.

• I have overdrive on my Chrysler Sebring and I too was told to leave it on, but I was also told that it can result in trani problems in the long run.. so in the city I keep it off. On the highway I turn it on.. If you need to pick up speed fast.. turn it OFF, then accelerate (that was right out of my owners manual)

• Overdrive adds a cog electronically, so you do not need to de-clutch to engage OD, (for those in America a clutch is the extra pedal on the left). OD will normally be available only on the top two (maybe 3~) gears (on a real car not an automatic). If used correctly, it will save fuel and lower engine noise (revs) and should only be used at steady speeds or under gentle acceleration. It decreases the available power and shouldn't be used for overtaking. It will not give a higher top speed than top gear (top speed in top gear with OD on will normally be lower).

• OD is designed only to be used on the freeway. Not in town driving. If you use OD in town driving, you will cause more wear to your transmission that you need to and you will not gain any MPG. This is how I determine when to use OD. If I am in the city, it is always off. (And for those of you who own cars that have an automatic OD, most times the OD is designated by a "D" with a square or circle around it.To avoid using an automatic OD (if applicable) shift the shift lever to 1 place below the "D" with the extra marking, to the "D" with no markings.) Then to shift into OD on the freeway, simply move the lever back up to the "D" with the markings around it. OD is only useful on mostly flat terrain, and under gentle acceleration, if any at all. It is not advisable to use OD when entering the freeway, as anything can happen, and it takes more time to drop shift from OD to 3rd (or 4th) gear than it would just to accelerate. Drive until you are moving at a comfortable speed, then move the shift lever to the "D" with the markings, or in push button vehicles, press the button. Using it this way, will maximize efficiency, and will save wear and tear on your transmission.

• Overdrive does save a lot of gas on open terrain, but it is not very good for the mountains where I live. Never use under 35 mph, as it is best after shifting through 3rd or 4th to pick up speed then use OD.

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