forte fuel injector cleaner and replace the fuel filter got mine up about 2-4 mpg
but with all the motorway miles i have done recently the ecu has learnt its way to better fuel efficiency as you saw 57mph over 200miles =42mpg
thats a lot higher than it normally is but then theres 700+ motorway miles into the equation in the last 2 or so weeks
i find even around town if you stick to lower than 3k rpm and get your gears right you can play the get more mpg game on your trip computer
I average around 32-34 and most of my driving is around town, 88k on engine and i do hammer it on quite regular but if i go for a long drive on motorway cruise control on at 70 I'm averaging around 40-45....
I go to the BTCC every year at knockhill and the drive from the boat (Stranraer) to Dunfirmline (last year was first time in the Veccy), I sit at a constant 60mph (boat arrives at 7am, need to kill time lol) and I average over 55mpg, got over 550 miles out of the tank last year!!