Why do people drop automatic transmissions from overdrive to drive in a city?
A friend of mine practices this regularly. He even goes so far as to do it for you if you’re not doing it while you’re driving (provided you have a floor shifter)
The reason I’m asking is that I’ve run across more and more people as I travel that believe this, too.
According to my friend, it’s to conserve gas mileage at lower-than-highway speeds, but so far as I can tell, giving your vehicle another gear to work with would cause your engine to be able to operate at a lower RPM, thereby causing lower gas mileage.
In all honesty, I thought the use of 1/2/3 or L as opposed to OD or whatever the highest gear is was for towing purposes for more torque, especially going up hills, not as a gas mileage conserver in sub-55mph zones.
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Filed under Gas Conservation FAQ by on Apr 23rd, 2010. Comment. 
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Comments on Why do people drop automatic transmissions from overdrive to drive in a city?
The owner’s manual to my car said to leave it in overdrive for intown driving for maximum fuel mileage.
This came from a government site on conserving fuel while driving.
Use Overdrive Gears
When you use overdrive gearing, your car’s engine speed goes down. This saves gas and reduces engine wear.
http://www.fueleconomy.gov/feg/driveHabits.shtml
To save gas, overdrive is mainly used for the freeway.
OD is intended to use at cruising speeds without a load on your vehicle. They are not intended to use at low speed or when pulling a load. Your vehicle builds up more heat in OD.
Also using OD in the city will most likely make it shift constantly anouther high wearing fact of a transmission.
I serriously doubt you will notice any milage change either way.
in all honesty it probably doesn’t make a difference… the only difference is what gear the tranny is limited to… if you put it in 2 then the tranny will not shift above second gear…drive the tranny will not go into overdrive…doesn’t change the shift points or anything like that so it really shouldn’t make a difference at sub-55mph zones.
Driving around town at lower speeds in overdrive will make the car more sluggish and you use more fuel, and less responsive to acceleration, in other words it struggles because it is a higher gear, i only put mine in overdrive when i am doing 80km an hour or over, anything under that and it wouldn’t pull the skin off a rice pudding.
My vehicle has overdrive and the way I understand it, from the owners manual is if you are going less than 35 MPH, then you do not need to use the overdrive. Anything over that you should use the overdrive, to keep the RPM’s down, and give your vehicle better performance. The gas savings is when you use overdrive, and you are going faster than 35 MPH, better performance meaning better gas mileage.
this harks back to the bad old days when overdrive transmissions were fragile. if you overloaded them by too low speeds in od or to much torque in od, the transmission would drop its guts and not work at all.
in these modern times, with transmission and engine computer controlled and built to a much higher standard, this stiuation doesnt happen anymore, so the ‘shifting out of od in the city’ doesn’t need to happen anymore
it is harder on a tranny to keep shifting while driving in a city so u take it out of overdrive to reduce the strain on the tranny
dick faber is exactly right. there is never a need to put your shifter in anything but overdrive unless you are towing. trans control modules control all the shifting, and they will not allow the trans to hurt itslef.