2009-2015 Cadillac CTS-V General Discussion Discussion, Gas Guzzler Tax Changed in Cadillac CTS-V Series Forum - 2009-2015; Maybe a bit lower than the ZR1, after all, it weighs a thousand pounds more....
Smart cars in the US are great, at least they were last year before the dealers opened. You got more attention pulling up to the club in one than a Ferrari 360. Pretty amazing. Guess they're not so useful anymore.
I dug a little further, and it appears that the GMPricing site has been updated to reflect a $1,600 tax for the Manual, and now shows a $2,600 tax for the Auto.
You certainly have access to more information than I do; please don't take this the wrong way. The numbers don't seem to add up right, though. There are sites online that let you calculate engine RPM for a given set of inputs: wheel diameter, gear ratio, final drive, and road speed.
If we assume a fixed road speed (65MPH) and a fixed rear tire size (about 26.85inches), we have two variables left: rear end ratio and final drive. For the manual, those two numbers are 3.73 and .63 respectively. For the auto, it's 3.23 and .67 respectively.
Given the road speed (65MPH) we'd get 1911RPMs for the manual and 1760RPMs for the automatic. A difference of about 150RPMs at 65MPH. The only difference between the two cars at that point is overall mass (the auto expected to be a tad bit heavier than the stick). However, at steady highway speeds, mass doesn't really come into play.
So, in the end, the stick SHOULD have worse gas mileage on the highway than the auto because it's running at a higher engine RPM. My guess is the city mileage is slightly in favor of the manual given the mass and the gearing (city driving is where mass comes into play).
Do you have the official EPA numbers from GM yet? All I see are the estimates on Edmunds, which I don't believe.
^ the stick SHOULD get worse gas mileage but its stated as slightly higher in the documentation given to the dealers. We have to remember that obviously the manual has less parasitic loss the the automatic. Especially since the automatic isn't even a true dual clutch system.