the hold switch basically has the same functions as the OD switch. in most a/t cars, when the OD is turned off and gear shifting is limited only up to the 3rd, the shift point is usually at a higher rpm. this will result in faster acceleration at the drive gear and, of course, make the car less fuel efficient. just put the shifter on "D" with the OD switch turned on or the HOLD at off during normal driving.