i bought my car used, with about 10k miles on it. i'd like to add that information to my car. the trouble is i don't know what kind of mileage the previous owner got... though i have an idea... when i bought the car the one of the trip odometers had about 1k? on it and the mpg was about 35. i could just add 35mpg/10kmiles... but i don't want to bring down my average. is there a way i can change the number of miles i started with without giving the mpg? i'd like to show that the engine had already been broken in.