metric tools - not so dumb question?

[George Harris]

In Canada, which has officially gone metric, many of our socket and 
open/box end sets are sold in combination Metric and Imperial sets. 
There are ratchets and johnson bars with 1/4", 3/8" and 1/2" drives that 
fit both the Imperial and Metric sockets. I rarely use the Imperial 
sockets since I am working on mid eighties Jags and Audis. In fact when 
I work on neighbours American iron; Dodge, Chev and Ford, I use all 
Metric as well.

The tolerances built into nut sizes and wrench sizes mean that even if I 
am working on an Imperial nut, I can probably find a Metric socket that 
fits just as well as the Imperial socket. Especially if there is a layer 
of rust to take up the slack, or after removal, to allow a slightly 
tighter fitting Metric socket to fit.

I was taught and raised in Imperial, but all of my children were raised 
in Metric. I sometimes find it a bit confusing when I talk to them 
during a construction project because all of our construction materials 
are still in Imperial ( 4' x 8' sheets of plywood, 2" x 4" lumber, studs 
on 16" centres - note Imperial spelling ;-) ). When I ask them how short 
a piece is, I get an answer in Metric and then have to convert to 
Imperial by dividing by 2.54 to convert centimetres into inches.

We adults still talk about 'mileage' while the kids are just so confused 
they don't know how to calculate it anyway. The official rating is 
litres per hundred Kilometres.

How is gasoline usage calculated in Europe?

Cheers
George