According to fueleconomy.gov, the 2011 NAH gets lower fuel economy than its predecessors: 33/33 mpg city/highway vs 35/33 before. Reports say that Nissan did not change things for the 2011 model year, so I'm curious as to why the 2 mpg drop. I don't see that the EPA testing methods changed either. Anyone know?

I've been wondering about that too! I drive a 2011 NAH.

I believe the numbers for the model year 08 to 10 NAH were converted by formula to the new method, but it seems for 2011, they're requiring the full 5-cycle test for some cars.

From http://www.epa.gov/fueleconomy/regulations.htm, take a look at the links to http://www.epa.gov/fueleconomy/420f06009.htm and http://www.epa.gov/fedrgstr/EPA-AIR/...ay-01/a451.htm and search for 2011.

From the 07, 08, 2010 and 2011 data files at http://www.fueleconomy.gov/feg/download.shtml, I looked up the NAH and the unadjusted (unadj) city, highway and combined numbers are the same:
46.8 46.6 46.7098

However, in the 2011 file, I notice extra columns and these numbers:
City 5-Cycle Unrd Adj - Conventional Fuel
Hwy 5-Cycle Unrd Adj - Conventional Fuel
Comb 5-Cycle Unrd Adj - Conventional Fuel
33.0977 33.2992 33.1881

06 Toyota Prius, had 04 Nissan 350Z; mom has 07 NAH