91' s-10 gas problems

i have a 91' s-10 2.5 four cylinder and the gas mileage is really bad on it but it runs good like nothing is clogging or stopping anything up so i'm not sure what it is. appreciate any suggestions thnx.

Welcome to AF.

Might try replacing the O2 sensor.

I have the same motor in an '86 Cutlass, it's a Pontiac Iron Duke and a great, reliable motor.
Is the Check Engine light on?
Has it had plugs & wires changed? Air filter?
The catalytic converter does eventually go bad and clog up the exhaust system.
32 psi in the front tires and 30psi rear? Are you hauling around any junk...uhhh, excessive weight?