I'd guess the average is higher due to a few factors. First being that people, on average, don't keep a car nearly that long. Average ownership (after a quick s

I'd guess the average is higher due to a few factors. First being that people, on average, don't keep a car nearly that long. Average ownership (after a quick search) seems to be around 5-7 years. Another thing might be your fuel economy given the most popular "car" in the US is a pickup truck. Also there is the cost of insurance, which I'm not sure you counted.