PaleMelanesian, I think "lockup" was the key word. My first vehicle with TC lockup was an 86 3-spd Chevette. Normally 30-35 mpg highway until, after adding a tach and so being able to monitor the lock point, I found 40 mpg could be repeated. Ever since then all my automatics sported a tach! Now the ScanGauge is even better. It paid for itself Year 1 towing a camper. Now into Year 3 I'm just reaping bonus.
Cheers
KB