Yoshi - do these new SuperMIDs have the feature that the calibration affects all the litre / km numbers?.
88HF - if not, it might be an idea, to make up a table so that you know how many real litres a SuperMID litre is, and how many miles a SuperMID km is.
This is what I have done on mine ; (FYI, 1.6 uncalibrated SuperMID litres is 1 litre in real life on my car, and 1.0 uncalibrated SuperMID km is 1.2 miles in real life!.
I have then just continued to push for higher and higher numbers - on my car, 6.9km/l (SuperMID) = 60MPG (imp). I haven't bothered to calibrate it as I am happy with it as it is!
P.S. 50% engine-off is pretty good