i have a 1992 pontiac bonneville. and im getting 14-15 mpg. im pretty sure its not supposed to be that low. put fuel injector cleaner in last april. any ideas on why its so bad?

Hi Gary when is the last time you gave your motor a tune up? Where are you from?
plugs
wires
O2 sensor
Air filter
Fuel filter
cleaned maf sensor

Check all Todd mentioned, but also check your tire pressure, and brakes to make sure they are not hanging up a bit.

.....also check all vacuum lines and connections under the hood

i live in michigan.
i replaced the plugs wires air filter in april.
i bought a maf sensor form a junkyard in june i never cleaned it. how would you clean it?
O2 sensor and fuel filter no.



DANTHURS what do you mean by the brakes hanging up a bit?

https://www.gmforum.com/normal-maintainence-138/cleaning-maf-sensor-278926/

Jack up the car and spin the tires. Do they turn freely? If a caliper is hanging up the brakes will drag and kill your mileage.

our tech info has a great write-up on how to clean your maf......EDIT....^^^^^^Dan got here first

alright. thanks danthurs. you might know this one too. everytime i press the brakes. they lose pressure and then i have to re pump the brakes. does that mean i need a new brake booster?

Sounds more like a master cylinder/hydraulic problem than a booster problem.

Try bleeding the brakes first, if that don't work then you will need to rebuild or change the master cylinder.