I did a oil change using honda 5w-20 for older cars (for the first time) and also did a tranny fluid change using honda atf ofcourse and now i am getting some impressive mpg. I can feel the difference right away when i step on the gas.

I know my car takes 17gallons to get a tull tank.
How come when the tank is full I have to drive for at least 35 city miles so the gas needle can finally start moving? I know there are about 3-4 gallons left once the E light is on, but when u have a full tank the needle goes a little above the max.