your car is showing no other symptoms then this???? there are multiply reasons a car could get bad gas mileage but almost all come with symptoms a driver can either smell or feel. having no syptoms is also a clue but you need to be far more detailed in your post on what exactly is going on if you want us to help. if this is your second thread on this issue post back to the original or copy the original posts syptoms here. your shifting isnt the problem though. your shift is controlled by your computer wich is set up to shift your tranny at different speeds or rpms depending on how hard your pressing the pedal.