Bad Gas mileage. I am getting around 12 - 13.5 mpg around town. 5.2 4spd auto. 90K miles. Thoughts?

These are ideas only as there are many things that could improve gas mileage.
When was the last time you had a tune up? (Spark plugs check for bad sensors . When was the Air filter changed..
do you always check the air pressure in the tires. Low tires can bring your mileage down five miles per gallon or more.
Do you drive with fast starts and stops.
Do you run short trips? Short trips does not let the engine warm up to the right traveling temperature. I live in town and I get about 15 miles per gallon in town but if I drive 20 miles or more I get 24 or more with my Buick.
You will get less mileage if you drive in real cold weather.

air filter? checking the octane rating of your fuel? tire pressures? theres so many things that alter mileage. is ur mechanic jeep certified?

I also have a Chevy Captiva 2L Diesel but with the auto box. The MPG on that one is abysmally bad! I bought it a few weeks ago with just under 30K miles on the clock (2007 model), and it returns around 230 miles on a full tank! That's around 17 MPG and probably on par with a Hummer!!
I was expecting the auto box to be less efficient than the manual of course but not to consume twice as much. Anyone out there with any ideas as to why this could be? I was actually already checking under the car to see if it loses fuel... We live in the suburbs and our trips can be considered a mix of urban and extra urban (they are admittedly on the short side and from a cold winter start; still, this doesn't justify the extremely low MPG). The car seems adequately powered for its weight and considering the small'ish engine and auto box.
Thanks!

15 MPG around town and 20 MPG highway.

hey...i have geos...since 1991....maded for econony and high gas mileage mainly
with those miles...shop around and unless you are blessed with the money to go name brand...i would get the lowest cost i can find...geo's are always gonna be in my driveway cause i can work on them interchange parts and get around cheap....jst my thoughts...i have a 94 metro...will not sell...offered much than its worth but when gas starts going up she will be back on the road again.....!

I have the same issue of low gas mileage. My 2008 Kia Rondo with V6 (2.7Lt) gets 20-21 mpg in average. Even for highway mileage, it is around 21-22mpg. Very poor gas mileage. Disappointed. I hope it would improve in the future.

You should be getting close to 360-390...depending on the type of driving you are doing. Increasing your gas mileage could be as simple as getting a fresh oil and filter job, change your air filter, change your fuel filter...and a biggie believe it or not, make sure you have the proper tire pressure. This will kill your mileage faster than anything else.

City MPG: 16-18 mpg
Combination MPG: 18-21
Highway MPG: Approximately 26 mpg

change your spark plugs if they haven't been changed in awhile. check your tires for the propper psi there should be a sticker on the inside of your drivers door that will tell you recomended air pressures go by this not the recomendations on the tires. also where are you getting you gas does it contain ethanol sometimes this can burn faster.

A really dirty air filter will knock down your gas mileage greatly....yes. Also keep in mind that you don't get as good of mileage around town, as you do on the freeway.....35 mpg isn't too shabby....oh and please give me a rating....thank you

i have never seen this before but if it was not operating properly you would a check engine light on