The test is measuring emissions, not efficiency. From the link: The Results During the FTP 75 test, exhaust gas from the vehicle's tailpipe is captured and ana

The test is measuring emissions, not efficiency. From the link: The Results During the FTP 75 test, exhaust gas from the vehicle's tailpipe is captured and analyzed by laboratory-grade equipment that's so expensive it makes the Kentucky Derby look like the Pinewood Derby. This lab equipment measures all kinds of compounds coming out of the tailpipe but the three we will focus on are those with which EPA and CARB are primarily concerned, namely, non-methane hydrocarbons (NMHC), oxides of nitrogen (NOx) and carbon monoxide (CO). (then there's a table listing the results...)