If you were curious how much gas this saves I tried this with my wife.s G-wagon which doesn't come with the ASS because who wants a V8 twin turbo that saves gas anyway?
In super sport mode in gear at idle it uses .7gal/hr, in comfort mode it uses .5gal/hr and in neutral it uses around ,.3gal/hr.
Same thing happened to me at the local tire dealer with my Porsche. It makes me think that you need check to make sure they put all the lug bolts back on lol.
Seems like a lot of low end mechanics are lazy and sloppy. My suggestion is you find one whose committed to doing good work and stick...
https://www.caranddriver.com/reviews/a37103139/2021-ford-bronco-first-edition-v6-by-the-numbers/
Great pictures and complaints by Car and Driver about low mileage (who really cares, go buy a Prius) somewhere about 17 to 18 mpg.