The ECT button should two positions - normal and power. All it does it change the upper shift points of the transmission - so that the transmission will shift at higher RPMs with your foot to the floor, with the button pushed to "power" mode. Example - if your redline is say 6000RPM - in normal mode, the transmission may shift at 5000RPMs at wide open throttle - in power mode, the transmission will shift a little higher - maybe 5500RPMs at the same throttle application. Actually hard to feel this work at all - difference is minimal. In normal driving - you should not see any difference in fuel economy or engine performance. Unless you drive around with your foot buried in the carpet all the time - in that case, power mode would decrease fuel economy. Towing may benefit - as you can hold a higher RPM level in a particular gear. Though you would get better gains with just turning O/D off - that will keep the transmission from "hunting" around between the top gears at highway speeds.