Starting with my first car in 1967, in Canada, I keep records not only about my car services but also on gas consumption. This helps me to follow a car’s general condition and to diagnose when my car needs a minor service, like an oil change. You know, your favorite car service would like to ‘see’ you very frequently. For instance, they’ll tell you that Honda recom-mends an oil change every 3500 miles which is not true; Honda says "at least every 7500 miles or less, depending on driving conditions". How does your serviceman know that you always drive at conditions which are much worse than average?