Unusually good fuel economy WTF?

[DOOK]

I usually drive with the economy on the display.
Normally I would see 11l / 100 km.
Today, on my way out of the city, I noticed it was dropping.
On the freeway, it dropped further finally reaching 7.3 l/ 100 km.
The Cruise I was driving as a courtesy car was getting 9.

Coolant temp was 192f.
No warning lights, or other strange readings.
I have never seen this good economy from this car.
WTF?

[fp115]

That sounds about what it should be on the freeway. Should be getting about 7.7 if you have an auto.

[DOOK]

I have an M6. I will only see 7's if I am doing about 1000-1100 rpm in 6th at about 65-70 kph.
It started dropping in the city, which was odd. I was taking it pretty easy on the freeway but doing 90-100kph.
It was still falling off the freeway, and up the hill to my house.
Very odd.

I have about 130k's out of a full tank so it shouldn't have been that sensitive to change still.