what could be the culprit for getting only 16 mpg compared to 24-30 previously. good maintenance habits, new plugs, filters etc. and still no help

get a tune up, check your tires, put air presser too 32psi, fuel up with 91 plus octaine for two tanks , flush your tranny, get a fuel injection service with "bg" fuel injection kit

the tune up is good, also check your O2 sen. i believe auto zone checks them for free.

check for a vaccum leak as well, O2 sensor and coolant temp sensors.

Folks, all those sensors and what not that you want him to check would cause the check engine light to go on if something went wrong. Have you changed your driving habits at all? Are the plugs and filters properly installed? Any recent modifications to the engine/drivetrain?

Avoid ethanol "enhanced" fuel like the plague. It's less efficient, so you'll use more of it.