Brett here.
The only reason NOT to use economy mode is if at least two of three things are happening at the same time-- engine coolant temperature is rising AND/OR you don't want to have to manually downshift (down arrow) AND/OR speed is dropping more than you want (and are willing to pay a lot more fuel for a few more MPH). Sorry, I know that is a mouthful.
But, we are back to the root question-- are you (and are you interested in being) smarter than something that can only see what has happened BEHIND you.
There is no right or wrong answer. I drive a manual transmission car (has have been the vast majority of my vehicles over the last 40 years) and am used to being proactive. Can I beat most others in MPG AND, repeat AND shortest drive time-- YES.
But, there is nothing wrong with saying "I bought an automatic, let it do its own thing".
The only time EVERYONE should use the down arrow is if you are climbing a grade and the transmission is "hunting". That is shifting between gears-- can't quite make it in the higher gear, so downshifts, then upshifts, then downshifts.......... Bad for any transmission. Use the down arrow to lock the transmission in the lower gear until the grade eases.
The beauty of the Allison is that you can drive it as an automatic, or you can use the shift pad to make it work like a manual.
