MPG Disappointment

Augustus

Regarding the Porsche Boxster Vs. 370Z comparison, pay attention to what you're actually comparing...

A Base Boxster has a 265hp 2.7L engine*. It's rated @ 30mpg highway. $50K
A Boxster S has a 315hp 3.4L engine*. It's rated @ 28mpg highway. $61K

A Base Cayman has a 265hp 2.7L engine. It's rated @ 27mpg highway. $52K
A Cayman S has a 320hp 3.4L engine. It's rated @ 26mpg highway. $62K.
A Cayman R has a 330hp 3.4L engine*. It's rated @ 27mpg highway. $66K.

*These engines are newly Direct-Injected, which accounts for their MPG improvement over the other engines.
(And no, this isn't from memory, I'm looking at porsche.com for the numbers)

A 370Z has a 332hp 3.7L engine. It's rated @ 26mpg highway. $33K. No direct-injection.

A base Boxster should trump a 370Z's MPG because its engine is direct-injected, a liter smaller, and produces 70hp (and 60 ft/lbs of torque) less than the 3.7 in the Z.

If you want the ~330HP & similar torque that a 370Z brings to the table, you've got to look at a Boxster/Cayman S or better. At that point, you're within a couple of MPG of a 370Z. A Cayman S, is exactly the same @ 26mpg. 1-2 mpg differences are quite irrelevant, as the difference will vary much more than this by driving style, driver, conditions, etc. And especially when we're talking about $60K+ cars, who cares about 1mpg more or less?

Am I happy with my Z's fuel economy? Yes. The EPA window sticker on my 2011 370Z MT says 18 city, 26 highway. With 6,700 miles on my odometer, I'm getting 16-19 in the city (highly dependent on the trip distance & my right foot). Steady, 70mph cruise-control highway with negligible wind, I'm seeing ~27 mpg. This is stock + K&N drop-ins, if that makes any difference (which I doubt).

I would humbly suggest that if your Z is literally only getting 20mpg on the highway, something may be wrong with your Z. I'd get it checked out.