Wide-open throttle but at whatever revs correspond to the power demand and with the torque converter locked so that it doesn't throw it all away as slippage.MadBill wrote: ↑Thu Apr 19, 2018 3:55 pm For what it's worth (ignoring power enrichment, which may or may not tilt the scales) an engine is more efficient at WOT than at any part throttle %, due to reduced pumping losses. This is the physics behind cylinder deactivation, small engines with turbos and Hypermilers who accelerate at WOT from very low to low/medium RPM and then coast.
My van has a modern engine and relatively modern automatic transmission. If an uphill starts getting steeper it will stay in top gear (6th) with the torque converter locked until full throttle in 6th with the converter locked doesn't deliver enough power, then it starts downshifting until it finds one that does deliver enough power. The torque converter is always locked in 6th and most of the time in 4th or 5th.