Does anyone know what the service interval calculation is based on? We all know it fluctuates, and some of us shiver at the thought of changing the oil strictly on the service intervals. I thought I read somewhere a few years ago that the service interval was based on gallons of gas consumed, and it multiplied that number by your average mpg to come up with a distance. Google search of NAM, motoringfile, and Mini2 didn't turn up anything. Can anyone support that theory or am I just losing it?