The 2013 Acura TL fills two roles, as a luxury sedan in base form or as more of a sport sedan in SH-AWD trim. And in both of those cases, gas mileage is neither tremendously disappointing nor very good.
Base 2013 Acura TL models with front-wheel drive get a reasonably good 20 mpg city, 29 highway; but SH-AWD models with the somewhat larger 3.7-liter engine and all-wheel drive aren't nearly as frugal or efficient. With the automatic transmission, models with SH-AWD get 18 mpg city, 26 highway, and with the six-speed manual gearbox it's rated at just 17/25.
We should note that we've as well or better than the EPA ratings in the SH-AWD models; in one with the manual gearbox we averaged nearly 23 mpg in about 400 miles of cold-weather driving--about two-thirds of it on the highway.