"Do you have data to back this up?" Official data (source: https://www.mazdausa.com/siteassets/pdf/features--specs/2016/mazda-6/2016_mazda6_features_specs.pdf h

"Do you have data to back this up?" Official data (source: https://www.mazdausa.com/siteassets/pdf/features--specs/2016/mazda-6/2016_mazda6_features_specs.pdf https://www.mazdausa.com/siteassets/pdf/features--specs/2016...) * Mazda 6 2.5L SkyActiv-G MT: 25/37 MPG * Mazda 6 2.5L SkyActiv-G AT: 26/38 MPG (28/40 MPG in Grand Touring model, not available in MT) As for the torque converter inefficiency - that is true only for some ancient transmissions. A modern torque converter will waste some energy only during shifting the gears. After synchronization, the torque converter is locked and the connection between the engine and the wheels is mechanical, just as in MT. "It's well known that accelerating rather quickly to your cruise speed is the optimal strategy for fuel efficiency" And now - any data to back this up? I don't have hard data, but I have some hard theory. Modern engines have variable valve timing technology which allow them to work in a much more efficient thermodynamic cycle when under light load and low RPMs. When you're not using the full torque of the engine it works in something like an Atkinson or Miller cycle, with high compression ratio and much higher thermodynamic efficiency. A bad thing about Atkinson-like operation (achieved by keeping the inlet valve open longer than normally) is that it reduces the effective capacity and hence power of the engine. So if you press the accelerator pedal fully, the ECU switches the engine to a classical Otto cycle, which is less fuel efficient but gives more power. Hence, if you accelerate fast, your mileage will be worse, not better. Another issue is that keeping high RPM at low gear (possible with turbocharger running on full pressure) to accelerate fast makes it harder to control burning all the fuel efficiently because there is less time to do that in each cycle. And also the temperature of the cylinders goes quickly up which makes it harder to avoid detonation. So in order to not destroy the engine, the ECU will adapt the injection / spark / valve timings and lambda coefficient to avoid explosive burning of the fuel by decreasing the effective compression-ratio and increasing lambda to decrease the temperature. Lower compression-ratio and higher lambda means lower fuel efficiency. That's why when I "eco drive", the ECU keeps the gear extremely high, so that the engine works typically in a range 1000-1500 RPM. Now this is quite hard to achieve in practice when driving an MT car, because whenever you want to accelerate faster, you'd have to gear-down by 2 or 3. That's why ATs are better for fuel efficiency. BTW: I do own 2 cars, one with MT, one with classical hydrokinetic AT, so I have a comparison. I'd really not be able to drive my MT car using such high gears as my AT car can. And also I can't switch gears so fast as an AT can do, even though my AT is not the fastest among all ATs.