acdii Report post Posted March 1, 2014 So if I were to get a new car in March, and the weather is cold, I'm probably going to get bad mileage forever unless I do a hard reset in the spring?Not necessarily, If you can maximize the FE when you first get the car, then once the warm weather kicks in and the fuel blends have less benzine in it, then the MPG will climb. If you can get 38 in the cold weather. you should have no problems getting 43+ in summer. I say 38-43 since it is what I get on average which is mixed city highway with lots of hills and stops. If your trips are at lower speeds with flats and fewer stops it can get much higher. Quote Share this post Link to post Share on other sites