V70 surprisingly high mpg

[emtor]

Volvo V70 - 2008 - 2.4d - 163 bhp.
I've been driving my V70 in Sweden for the four last years and never managed to get the mpg better than about 43 mpg (imperial), motorway driving.
After moving back to northern Norway my mpg increased to 59 mpg.
Why the sudden increase?
Well,-there's two explanations:
-Speed limits on the motorways in Sweden is 110 km/h (68m/h), while in northern Norway the upper limit is 90 km/h (56m/h).
So reducing speed seems to help a lot.
Another factor is what they call 2+1 roads in Sweden, when on the motorway they alternate between one and two lanes. When there are two lanes in your direction there's one lane in the other and vice versa. It saves money when building roads, but there's a snag: When driving along in the single lane in northern Sweden you're sure to end up behind a truck hauling timber with a speed limit of only 56m/h.
So, on a one hour drive you've been accelerating past about ten of those trucks once the road changes to two lanes in your favour.
The solution: -Move to Norway.

[krzemien]

Upper speed limit is definitely a consideration - but indirectly, as it simply translates onto engine revs.

These then are subsequently also lower, and possibly (and very likely) in the examples you quoted do not engage turbo to large extent (which normally contributes to increased fuel consumption).

If I remember correctly threshhold sits somewhere between 1,500-1,800 rpms (depending on the exact model, engine etc.).

[Georgeandkira]

"Upper speed limit is definitely a consideration - but indirectly, as it simply translates onto engine revs."
Don't forget wind resistance in your calculations. It contributes a lot.

Personal experience: The only diesel vehicle I ever drove was an ancient Mercedes-Benz sedan (4-door...forget the model) in Sweden on 2+1 roads.

Passing the pokey logging trucks with the slow diesel was challenging.

[FreshAir]

Speed is the change. Aerodynamic drag is function of the square of the speed so changing speed makes massive and the main difference.

Engine friction is directly proportional to engine speed to in same gear directly proportional to speed. Some increase in engine pumping losses not directly proportional to speed, also could be slightly richer mixture at higher engine load which reduces engine efficiency.

Bottom line is the vehicle speed and aerodynamics is by far biggest change and the reason.

[krzemien]

I certainly don't discount aerodynamics as such, however I still believe that in the quoted example vehicle turbo - at least in this speed range - is the main contributing factor.

[Jinkster]

Ive got a 2015 V70 D4 2.0 VEA engine. The average consumption on my journey to work the other day over 165 miles - mostly motorway was 65.9mpg. I was very early so drove between 55 and 65mph and no traffic on a Saturday morning.