89 4 cylinder coupe, gas mileage?

it may do better in real life. those are rounded estimates.

My 93 gt gets as high as 25 mpg on highway.
 
I have a four banger auto for DD and the A4Ld really sucks the life out of it.
even with a fresh tune up and properly inflated tires I am doing really well to get 250 to a tank :(
I would expect a manual to get closer to 300 miles to tank.
on the upside cruising at 80 on the interstate I did get 28 mpg.
 
Nice :)

The one I'm wanting to pick up for a DD is a 5 speed, tired of driving around a full size truck that gets 15 mpg in the city

DON'T!

I've had 3 in my younger years because I wanted to be cool and only drive mustangs. The 2.3 is highly under powered, can't get out of its own way, and backed by an auto is even more of a turd. Top that all off with the mileage not being great, and its not a good choice. Pick up a civic, and get a LOT better gas mileage.
 
In town, low 20s on the highway middle 20s. Not much better than a 5.0 on the highway, SLOW (I had the 93 too which got more power), and the insurance was actually more than the Jeep Grand Cherokee LTD I replaced with the 4 popper.

I would agree, a Civic or other small 4cyl would get much better gas mileage.