New tech autos actually deliver equivalent MPG as a standard, and probably better as you have to really drive a stick "softly" in order to maximize MPG.
Actually, it's pretty much strictly down to gear ratios now. Since the advent of the locking torque converter (which eliminates slippage at steady-state cruise) automatics have no real mechanical reason to be less efficient at cruise. The built-in slip of an unlocked torque converter also allows the use of taller gearing, which helps steady-state cruising even more.
Most automatics today are geared taller than their manual counterparts and this is why they get better mileage. In fact, it's pretty much the only reason.
The reasons for this are simple. Before the lockup torque converter, the slippage meant that manuals were much more efficient, so manuals were the choice for people who wanted maximum fuel economy and were set up with gearing to accommodate such. As lockup torque converters and 5, 6, or even 7 and 8 speed automatics came into the field, the older limitations of automatics (slippage and the inability to match the total number of gears in a manual) ceased to be factors. This allowed manufacturers to tune automatics for the same economy as a manual.
Once automatics and manuals got the same fuel economy, the only reasons to have a manual became price and sportiness. Since price is essentially no longer a factor (even where an automatic is "optional" it's often very cheap compared to other options), sportiness is now the primary reason for a manual. Because of this, almost all modern manual transmissions are geared lower than their automatic counterparts. This means better acceleration and a sportier feel, but it sacrifices fuel economy. The sacrifice is acceptable given the current market for manuals.
Basically, there's no inherent "new tech" that makes automatics more efficient. They're still technically slightly less efficient if the gear ratios are equal, but in practice the gear ratios are never equal because of the way a slipping torque converter effectively "creates" a lower ratio that can be engaged or disengaged by cycling the lockup clutch.
ZV