Too bad even in America the EPA can't ever seem to get the MPG rating right, comparing it to real world numbers it never stays in line with them
Actually, the latest US EPA protocol is very accurate for an AVERAGE driver. The protocol does NOT take into account a heavy foot, hypermiling, or places that have high speed limits.
There are exceptions to this. Most of the time nowadays, the manufacturers do the protocol themselves for the EPA. There are simply too many cars for the EPA to test individually in their factory. So, EPA relies on the "honesty" of OEMs to do the protocol...probably witnessed by EPA employee i assume. EPA will only re-test a vehicle if consumers question the EPA rating of a car.
This is why from time to time, you will see EPA ratings changed from year to year on the same car. This is because EPA went back and re-tested the car and thus had a different result from OEM testing. Classic example...Toyota Camry Hybrid (prior generation). Toyota (following EPA protocol presumably) testing showed optimistic ratings...after a year or two, EPA came back and re-tested themselves and lowered the fuel economy ratings. I am not sure if EPA punishes these OEMs "errors" or not.