I've been using my mpg display to tweek my driving habits recently, seems to work, my tanks have been between 29 and 32mpg in mixed driving including alot of city driving, so I cant complain. One thing I've noticed is when I'm going down a hill or coating to a long stop, my mpg display usualy says 99, but sometimes it sticks at a lower point, say 65 or 70mpg. In this case a light tap on the gas with my foot it goes to 99. I'm wondering if I may have a sticky throttle body, TPS sensor or other? I know it sounds petty, but if it is something sticky, it may improve things even more. Anyone experiance this?

 

If the car is in dfco mode (not using any fuel) it will show 99. Sometimes your rpms won't be high enough to put the car in dfco while coasting, so it will read the actual mpg as its using fuel. That light tap is enough to raise the rpms high enough to put it in dfco when coasting in gear. If your throttle was actually sticking you would be able to feel it.