you need to tune up more often and change parts if possible. there is something called octane booster that WILL increase your mileage get your injectors clean throttle body service and you will see a big difference got money on that and on the heating problem try getting something called fiber glass it is like fur u put it under your dashboard against the fire wall this keeps the heat away any problem 18687793455 anton! this is one of d best cars nissan ever made just a little tlc the car needs