Answer:
First you have to find out how many gallons your vehicle holds. I will give you an example on my car. My 94 mirage holds 10 gallons of fuel so 1/2 is 5 gallons. When you fill up reset your odometer and do your normal driving until your half on your tank. take that number and multiply by 2 and divide what your tank capacity is. 5 gallons on my car equals 155miles times 2 = 310miles divided by 10 = 31mpg.