Two things occured to me:
1). If I want to pass and want a lower gear, I don't have to mash on the gas to get the car to downshift. I can just tap on the downshift paddle, and then pass, and then tap on the upshift paddle. Should save a little gas (I think -- I haven't tested that, as I don't pass that often).
Nope. If you downshift without mashing the throttle, the car slows, it doesn't speed up. The purpose of downshifting is to increase the torque multiplication by going to a lower gear, which allows quicker acceleration and faster passing. Best strategy for economy with an automatic is to allow it to think for itself.
Outcast_Searcher wrote:2). Downshifting to save gas via engine breaking. Similar concept to the regen braking mode in an electric -- not as good but the same basic idea.
Again, no. When you downshift, the engine goes to a higher RPM. If you have lifted off the gas pedal, the engine is running on the minimum gas used for the idle speed. Anything that increases RPM also increases gas consumption. Yes, the engine braking effect is greater, but so is gas consumption. Best strategy for economy is to lift off the gas and apply the brake pedal. Let your transmission shift as needed without any interference. Shifting gears under these light load conditions causes minimal transmission wear.
The purpose of paddle shifters is to increase acceleration performance by forcing the gear shift points higher than they would otherwise occur. The stress and wear on the transmission increase.
The fact that you are thinking about optimizing performance via gear shifting indicates that you should be driving a manual transmission. Such gearboxes are cheaper to buy, have cheaper routine and repair service costs, and higher reliability - as long as the operator doesn't make a mistake that damages the gearbox.