Mine is no larger than 100 litres. I drive city/highway and the computer reads 19 mpg. When I fill up, I see how much fuel I have used and divide it into how many miles I've gone and it reads around 19 too. This weekend I am on a highway trip, and hope to get 25 mpg (miles per gallon) or more getting me over 500 miles on a tank. I have heard from another 745 owner (not on the site) that his would get 26 on the freeway.