For those of you who don't know, I have known for a while, but all cars starting in the 2008 model year will be evaluated for fuel mileage differently than cars have been in the past. These are going to be "real world" tests, and not just minor simulations. Real cold starts, A/C on, higher speed limits, faster accelerations, etc. Larger engines will not be as affected as smaller engines, ESPECIALLY hybrids. The EPA'* fuel economy website has made an entire section showing the difference. They have integrated it into their catalog of fuel economy ratings all the way back to 1985, showing approximately what older cars based on the old testing should be getting in real world conditions.
1987 LG3 - Old: 18/27 - New: 16/25
1989 LN3 - Old: 18/28 - New: 16/25
1991 LN3 - Old: 19/28 - New: 17/26
1992 L67 - Old: 16/25 - New: 15/23
1994 L27 - Old: 19/29 - New: 17/26
1995 L67 - Old: 17/25 - New: 15/24
2003 L36 - Old: 20/29 - New: 17/27
2003 L67 - Old: 17/27 - New: 16/25
2005 LD8 - Old: 17/24 - New: 16/24 (4565cc N*)
Every year varies just a tad, so follow this link to check your own.