Another point to note is that the old EPA testing standards were extremely kind to all hybrids. They were run at a relatively low speed and with little or no sudden acceleration. This is what a hybrid just eats up because when run at a steady, low speed, the gas engine turns off and it runs on battery. Since the tests were run without A/C, there was no substantial load on the battery, and you got phenominal mileage out of it. Having said that, you have to remember that the EPA testing methods were created long before hybrids came to the market, and the hybrids just got lucky.
Whoever said that all vehicles lost about 20% was absolutely correct, but 20% of a Hummer that only gets 12 mpg is not very significant when compared with a a hybrid that was getting a rated 60 mpg! The Hummer is only going to lose around 2 mpg and the hybrid will lose between 12 and 15 mpg. That is why it looks as though there is a huge change, but in reality nothing changed but the method of testing.
The manufacturers are required to only quote the EPA mileage, if they quote any mileage at all - they are not allowed to make any other claims. That is why the Hummer mileage is conspicuously absent while the hybrids are more than willing to post theirs right on the sticker.
Those that whine and moan about how good the hybrid mileage is, and how poor the others look in comparison should take that up with the government, as the manufacturers ARE NOT ALLOWED TO USE ANY OTHER FIGURES. To claim that any manufacturer "lied" is so patently stupid as to be beyond belief, but about what is to be expected from that vocal minority of bozos who choose to post here without knowing anything at all about the subject question.
Point of fact: I own a 2007 Camry Hybrid and have owned it since May 2006. I get a steady 36.9 mpg on my daily commute of mixed highway/city driving and the highest that I have ever seen is 42.5 mpg on a long trip in flat country, and that was only for that one tank; I have never been able to duplicate it.
The 2008 Camry Hybrid is identical to the 2007 Camry Hybrid in every way but one: the price went DOWN for 2008!
Previous owner, 2002 Prius
Current owner, 2004 Prius and 2007 Camry Hybrid