Consistently about 5-8% higher than I'm actually getting in the real world. I've yet to come within 2mpg of what's been displayed and I've got over 5,000 miles and have measured every tank after the first couple partial fills. I'm still happy with the 42 mpg I've been getting. I was thrilled to hit 46.5 on my last tank until I filled up and calculated that my actual mpg was worse than my average! Funny how the computer never misses on the low side.May I know how is the mileage calculated by the computer?