The heat take too long to get warm even in the normal day (60's F). Sometimes when I started it and just stood outside and it was like somebody step do the gas and step off and step on and off, making the car like it is ready to race (like we see in the movie before the race they start). ANd it has worse mileage I ever seen: 14 miles per gallon!
What seems to be the problem?

check the air filter and change the plugs!

A thermostat stuck open will prevent the engine from warming up. it will also keep the engine in a state where it is trying to run a bit extra fuel into it so it will warm up faster.and is a cheep easy fix.