[Jason.MZW20]

Well the Tacoma will also encounter more rolling resistance, mechanical drag, and aero resistance than a FWD car. You know, there's more components causing drag on the drivetrain in a RWD vehicle. You have this rather heavy driveshaft trying to maintain motion, the pinion gear and ring gear inside the rear end, and the solid rear axle. They're all much larger in size than their transaxle counterparts. You also have these HUGE (relative to the comparative Civic) tires moving with a tremendous amount of weight on them (also relative). The A750 is programmed to provide more engine braking to facilitate stopping such a heavy vehicle. But on any downhill grade, even with the throttle pedal down, the ECU reduces the amount of fuel injected per cycle. Lift off the pedal and injection ceases and engine braking engages.

The RA60 manual transmission is a close-ratio box (made more for the X-Runner than other models), so you won't see the kind of MPG ratings or realizations of an automatic. However, having driven an automatic 4x4 Taco for a few years now, I'd say even though the gearing is longer, the engine needs more throttle loading (= more fuel) to accelerate in top gear (which it tries to be in AT ALL times), even on flat roads versus a manual.

Once you pass the 20% throttle limit on torque converter lockup, the torque converter will unlock, bumping RPM up 500rpm and causing more parasitic drag on the drivetrain again until it locks. The transmission essentially needs to downshift into 4th gear in order to stay efficient on relatively mild hills and during mild acceleration, but the transmission programming will not allow it. Instead, it unlocks the torque converter first, if that's not enough it will eventually downshift, but by that time the need has past.

The newer model years have received some torque converter lockup tweaks in the programming, so I'm not sure how much it differs now. My experience is with a March 05 model equipped with a replacement transmission and ECU (direct replacements).