Picked up my new Jazz EX Style on Tuesday and today was my first proper drive. Mostly dual carriageway and motorway, around 80 miles round trip with speeds mostly in the 60-65mph range topping out at 70mph. My average was 56mpg, I was hoping for 60+, so maybe it will improve a bit when the engine gets a few miles on it.
Its fuel advantage over other cars at motorways speeds is welcome but not as impressive as it can be in town and slower speeds. You really notice the fuel penalty for even a small increase in speed. (and saving for a small reduction in speed and a gentle right foot) But even at 70 mph you may improve on 56 mpg . Colder weather (a feature for the next few months 
) ) does increase fuel consumption. It does with normal cars, but maybe not as noticeable due to the consumption displays., Fuel consumption in warmer weather is what really brings a smile to your face. 
It can also vary quite significantly depending on whether there is a head wind or tail wind or the route is predominantly up hill or downhill. You may have been unlucky with the overall average on that particular journey I sometimes wonder why the car seems to be guzzling fuel for a while when the motorway or other road seems flat to me yet with no obvious change to topography, speed or battery level it might use no fuel at all. Best to give it more time to average out.
Some find adapting their driving slightly to the cars strengths can help. Easing back slightly, rather than going for every last bit of available power can reduce fuel consumption (and noise) significantly without noticeable loss of performance.
It was a windy day with some significant changes in elevation.
I just did a quick 2-3 mile each way, in and out of town trip from a cold start and achieved 56mpg, so that's pretty good, a journey that was always so inefficient in the Honda E, so clearly the Jazz is happier at town rather than motorway speeds.
I feel I am almost an expert of squeezing efficiency out of my vehicles, my previous BMW's 540i touring and X3 M40i, both up to 43mpg on runs, regularly in the 38/39mpg range and 50mpg on my current Volvo XC90.
The Jazz now sits nicely as our second car for short trips around town, whilst the longer journeys are catered for by the effortless comfort of the XC90(provided the end parking spot is big enough)
The Jazz is a much better overlap to the XC90 than the E having both a range and space advantage.
