my real world mpg is between 48 and 52mpg from november to april with 16" pirelli winter tyres. my summer mpg is between 54 & 56mpg with 17" alloys with falken ze310s. It used to be 54 - 59mpg on goodyear efficent grip. better fuel economy rating on the tyres.
I just leave it in normal mode, dont bother switching let the car do its thing.
Air con is on all the time and heated seats used in winter. all on sainsbury/tesco fuel. using vpower etc doesnt make a massive difference do the efficiency of the atkinson engine.
Drving is all town, a roads and dual carriage way at the speed limit. on longer journeys from stratford on avon to watford at the speed limit I usually see 52-55mpg in winter and 56 - 60mpg in summer.
to get the best on motorway/long runs you need to learn the coast and glide method with the car. My tyre pressures are also set 3psi higher all year round which will make a slight difference. any more than that and the ride is awful and increased tyre wear happens.
wheel alignment and tyre pressure is one on the biggest killers of mpg. the next is the calliper sliders seizing due to lack of strip down at dealer servicing - I lost approx 10% when this happened. egr valve issue will also hit the mpg by 10%.
If you sit at 80mphg on dual carriageway/motorway etc then the mpg drops off quickly after this.
Check what oil the dealer/servicing outlet has used. they are meant to use 0w20 oil but a lot of garages will use a more common 5w30 which again has a impact on mpg
Alex
Alex