Poor fuel efficiency in recently purchased Mazda Miata

According to the EPA, your mileage is just about normal -- 20 city, 22 combined http://www.fueleconomy.gov/feg/noframes/15609.shtml That said, it could need a tune-up, or it could be based on the speed you drive or how you work the clutch if it is a manual.

Check the oil, oil filter, air filter, etc. While the car was babied, it is always good to do some preventive maintenance. 18-22 sounds about right though some people report in the 30's. What is your driving like?

I WOULD DO THE REGULAR MAINTENCE THAT YOU SHOULD DO TO A USED CAR LIKE PLUGS, WIRES, OIL, OIL FILTER, AIR FILTER, FUEL FILTER THAT WAY IN A YEAR OR EVEN 5 YEARS YOU KNOW THE LST TIME THEY WERE REPLACED THATS WHAT I LIKE TO DO WITH USED VECHICLES USUALLY HELPS TO GET BETTER GAS MILLAGE BECAUSE ONCE THE FUEL FILTER IS A LITTLE CLOG IT MAKE THE FUEL PUMP PUSH MORE FUEL BECAUSE THE COMPUTER ISNT GETTING THE RIGHT READING WELL I HOPE THIS WORKS FOR YOU AS IT WORKS FOR ME

oxygen sensor values would tell you if something is wrong,and your check engine light would display if the parameters for fuel trim are exceeded,which i'm guessing yours is not,fuel filter and look at the pugs,air filter,also valve timing could be off if someone did t belt and missed one notch,but might set a code if that was so,look at the plugs,if they are clean,you need to try driving for economy one tank,add good injector cleaner every few months.

regular tune up and change oil will help a bit... it also depends on how fast or slow you drive, how hard you step on the gas for speed, gear change...