63 MPG! Well impressed!

[rwb]

The 407 2.2 petrol did 20mpg when used as a shopping trolley, but I got 46 out of it on my usual run.

It certainyl does depend on temperature. I offer the following two hypotheses:
(1) the car over-fuels itself when it's cold to try to warm itself up, and
(2) when the air is cold there is more of it in the cylinder and therefore the map allows more fuel to be injected.

[frog]

I have two other hypotheses to offer:

(3) Winter fuel has anti-freezing/-waxing/-clogging additives, making it less efficient
(4) Colder air is denser, giving more resistance while driving.