Driving technique is a lot of the problem I'm afraid
I have a 2015 240 L2 Limited with the 110ps engine, I'm fully laden at all times, I never turn the A/C off, my main journeys are 4 miles each way often in traffic, when I do a tank to tank on those journeys I get 38mpg when I go on a journey my mpg climbs according to the trip computer regularly to 45-50mpg, the furthest motorway journey I have done so far is Bournemouth to Kent, starting with a full tank, by time I got there I was reading 68.9mpg the return journey was a headwind all the way home & the computer had dropped to 66.2mpg my overall average since new is 47.1mpg My previous connect was 32mpg so I'm very pleased considering the short journeys & the weight I'm running at.
This is how I drive, I'm a former ex HGV owner driver where you become almost obsessed with fuel, 1/4 to 1/2 mpg gain in an artic at 8mpg is a serious saving over the course of a year:-) this apply s to my van with my gearing & engine & seems to work for me
look up the max torque & rpm figures for your engine where the 2 converge is you max rpm to change gear, go beyond that & you waste fuel
1st gear 7-10 mph change to 2nd
2nd gear 18-20 mph change to 3rd
3rd gear 30 mph, stick to this for round town driving, it actually helps you not to speed, use cruise control IF SAFE TO DO SO, for 40 mph accelerate to 40 mph change to 4th
4th gear 40 mph, again this helps you not to speed, use cruise control IF SAFE TO DO SO, for 50 mph accelerate to 50 mph change to 5th
5th gear 50mph, again this helps you not to speed, use cruise control IF SAFE TO DO SO, for 60 mph accelerate to 60 mph change to 6th if the terrain is up & down watch the average mpg & you will soon learn if you would be better of sticking to 5th.
When accelerating use 1/2 throttle, use the engine torque, the van gets there just as quick as flooring it everywhere, I don't drive like a granny I can assure you, rather than rush upto a junction obstacle or roundabout, lift of the throttle & use momentum, you save fuel, brakes & tyres.
Keep your tyre pressures correct.
Don't allow excessive Engine idling
Don't allow the engine to labour but learn how low you can allow the revs to drop & still be able accelerate without flooring the throttle.
Hopefully if you follow all or some of the above & with practice, you can certainly help improve economy