After 2 record tanks @ 4.16 L/100km (56.5 and 56.7 mpg), Hägar is going in for some maintenance and will be getting Vekke's Tungsten-sulfide in the oil.
The record tanks are due to one simple thing : driving even slower on the motorway while drafting trucks (at a safe distance) as often as possible.
See
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com ; # 35 :
Find/adopt a 'blocker' for slower freeway speeds
I've been down to 85 kph / 53 mph quite often, and it shows instantly !
Something else I've been doing more is driving 30 kph / 20mph in 4th at idle rpm, rather than using 3rd and CC.
Works only when the road is level, or going downhill.
There is only a limited distance I can do this, on only one way on my regular commute, so I don't think it'll affect my mileage a lot.
4.2 L/100km - 56 mpg used to be my mpg-target
The garage doing the maintenance will be reporting on the level of the soot filter's additive tank. I'd expect the tank to be nearly dry with the many regenerations of the DPF.
If it's not, then it's quite likely not dosing the catalyst to reduce the temperatures required to burn off the soot, and the root cause of the too frequent regeneration problems.