Mileage can often be a good indication of how a car has been used by previous owners. The mileage will usually be higher the older the car. An average mileage count per year should be between 10 and 12,000, higher than this is usually considered to be high mileage. It is also worth knowing that, with proper maintenance and care, a modern car has a life expectancy of up to around 200,000 miles.