In days gone by, the average life of a car engine was eight years or 150,000 miles. New designs, better technology, and improved service standards have increased this average life expectancy to around 200,000 miles, or about 10 years, in recent years. With an average mileage of around 10,000 to 15,000 miles per year, a three to four-year-old car will have around 30,000 to 40,000 miles on the odometer.