Using DFCO to increase your MPG

[Pavel Olavich]

Originally Posted by adamschneider

I drove over the mountains twice last week and experimented with engine braking quite a bit on the downhills. (I have an automatic transmission.) I was experiencing the same thing that AustinYaris mentioned a few months back: with the exception of a few really steep hills, downshifting to 3rd slowed me down way too much, so I was having to put it in neutral to pick up speed again. As I understand it, DFCO doesn't kick in at all when you're in 4th ("D") in an AT, correct?

So, basically, when going down hills, I was in 3rd gear on the steep parts (which had the dual effects of activating DFCO and slowing down the car so as not to get out of control!), then I would bypass 4th and go into neutral for the shallower inclines. I didn't use D unless I needed to give it some gas. Does this sound like the best way to do it?


EDIT: I just saw Pavel Olavich's most recent post. Pavel, are you saying that the Yaris AT does go into DFCO mode even in 4th gear?

I believe that keeping the shifter in D can activate DFCO if you allow the tranny to automatically downshift, caused by the "grade logic" of the tranny....in this way, your shifter is in D, yet the tranny is in 3rd, and DFCO can happen, given the right circumstances of course. When I find myself driving down steep hills, I tap the brake a tad, and this often causes the tranny to automatically downshift, and I think when it does this DFCO is happening....but my car does not necessarily lose speed...it often just holds the speed constant, and this is often what one wants in these circumstances.