OK, guys and girls ! I see I can't fool you .....

Just for the thread's sake, I have to rectify LED's calculations :
a Sancerre bottle is a bit more than 1.3kg. So total load (driver not included) for the car is in the 460/470kg range.
I didn't check my car's comsumption with such a load, at 80mph.

As for the 58mpg I mentioned, that's my car's average consumption all year round. I mainly drive in/around Paris and on highways (highest consumptions).
On smaller flat roads, at 56mph (max allowed), my car drinks around 5.5 liters/100km or less. More than I do ....