My Jazz 1.4es nearly 3 years old and 16k miles on the clock- average mpg from new is 54.8 on the computer. I did once do it the proper way by topping up tank and checking how many litres needed/miles travelled at next fill up, and it roughly corresponded to what the computer said, so I decided to get a life and use the computer. Even if the computer is optimistic as several members have said ,its not a bad fuel consumption for all my driving since new- a 10% optimistic computer still shows nearly 50 mpg, that's good enough for me. I try to avoid short journeys ( by using a bike), don't commute, and tend to stick to any speed limits. Driving to Portsmouth on mainly dual carriageways, about 110 miles can show up to 60mpg on that there computer, depending on how many road works with 50mph limits I have to drive through.