i have a 92 buick regal.i know on the highway its better on gas mileage in overdrive.what about just in town.slow speeds? also can i whicth from overdrive to drive while cars moving are should i wait tell i come to a stop?

The auto overdrive engage function, is controlled by the speed of the car and overdrive (4th gear) will usually not engage under 45 mph. It would not be wise to drive the car in “drive” at speeds in excess of 45 mph, due to the higher rpm requiring more fuel and generating excessive engine temperatures. It is ok to shift from OD to drive, while driving at lower speeds. If you are driving @ 80 mph, it might not be a good idea!:thumbsdow

The auto overdrive engage function, is controlled by the speed of the car and overdrive (4th gear) will usually not engage under 45 mph. It would not be wise to drive the car in “drive” at speeds in excess of 45 mph, due to the higher rpm requiring more fuel and generating excessive engine temperatures. It is ok to shift from OD to drive, while driving at lower speeds. If you are driving @ 80 mph, it might not be a good idea!:thumbsdow thank you.my car has a gear shift for drive and overdrive.so a low speeds should i leave it in overdrive?

thank you.my car has a gear shift for drive and overdrive.so a low speeds should i leave it in overdrive?
Yes, OD is fine. The transmission will select the best gear for your driving style & conditions.