2 part question my car uses too much gas and when shifting it takes 5 -10 mph to shift into fourth gear?

age isn't the problem with it,you need to have the transmission checked in it,and you may just need a really good tune up did on the engine to bring it back up to what it should be at,those are good cars and do get really good gas mileage when they are running right and its pretty obvious that yours isn't running right,have someone scan the computer also and see if it has any bad sensors on it that might could be causing this too happen,i don't think you have real serious problems right now with it,but have the scan did and see what it tells you about it,good luck with it.

your car's getting old. Even with regular tune-ups and good maintenance, it probably won't get the kind of mileage it did when it was in the 50k-120K mile range. 16 really isn't that surprising for an old car in city traffic. I would expect it to get high 20's on the interstate if you drive sensibly.

The trans question is also answered by the statement "your car's getting old." I would check the fluid level (with the motor running and after you've been driving it), and maybe add some Lucas fluid to it, but a trans with lots of miles on it will start to have problems.