The EPA actually has the testing results down to the 4th decimal point in this document.
CSV file dataset:
http://www.fueleconomy.gov/feg/download.shtml
Everything gets rounded to the nearest whole number.
V8 Automatic: 16.5112 city / 27.9892 hwy / 20.2477 combined
V8 Manual: 16.4354 city / 24.9093 hwy / 19.4062 combined
V6 Automatic: 19.4758 city / 27.9813 hwy / 22.562 combined
V6 Manual: 17.8527 city / 26.8969 hwy / 21.0357 combined
I was thinking that just maybe the V6 auto got screwed with rounding, but the V8 auto actually did better on the highway.
They did get screwed by rounding with the V8 and V6 manual city ratings, and V8 manual combined rating.