Its friday today n the roads in toronto are not as congested during the morning drive to work, SH-AWD V6, same route, 75% city driving 25% highway, econ mode, lots of hypermilling n coasting whenever possible (basically driving like a hybrid), easy on the brakes whenever possible at a red light (rolling stop), engine idle stop whenever possible, outside temp is around 7-9C, drove for around 45mins, max speed just below 60mph, A/C off 95% of the time, getting 9L/100km for my trip. 10L/100km city driving before entering the highway which dropped to the 9L/100km total
engine idle stop does not work for the first 5 mins of driving from a "cold boot", so i suspect the engine needs to warm up first before the idle stop can kick in. which also means when we reach sub-freezing temperatures this function may not work as frequently (if at all) as in the summer or even now.
so going forward, i will most likely leave the car under ECON mode while commuting or normal driving, certainly will not need the full 290HP on the engine in those cases. even though gas prices are temporarily dropping, it still ain't cheap to fill up the TLX for almost a hundred bucks. will put it in SPORT mode if i feel like speeding beyond 75mph or need to accelerate entering a highway ramp to get to highway speeds (but even then ECON is probably sufficient)
i would say under normal to slightly desirable conditions, the advertised city driving MPG is certainly achievable, if not better. canadian models are rated at 11.2L/100km for city driving and overall i am getting around that range (11L/100km or so), or even better if i am more conscious on applying fuel-saving driving techniques and if we are driving in warmer temperatures where the engine warms up much faster.
for this reason i am placing my vote on "better than advertised". may get even better if in the summer (A/C usage may affect mileage though)
i have yet to take long road trips to test crusing highway MPG, but i personally care about city MPG more than highway MPG