Fuel varies so much in price that fuel price variation would mask cost differentials between cars.
You could start combining some synthetic averaged fuel price with MPG to arrive at a cost. But is it a cost that anyone's likely to achieve, or know how it relates to their own circumstances.
At least mileage figures however flawed are a known quantity, I know how it relates to my driving, and I know whether fuel prices are currently low or high.
Fuel varies so much in price that fuel price variation would mask cost differentials between cars.
You could start combining some synthetic averaged fuel price with MPG to arrive at a cost. But is it a cost that anyone's likely to achieve, or know how it relates to their own circumstances. At least mileage figures however flawed are a known quantity, I know how it relates to my driving, and I know whether fuel prices are currently low or high.