Near my odometer are two pushbuttons. The left one controls various functions of the outside temperature-direction; average miles per gallon; etc. The one on the right changes the odometer to the miles on the vehicle, or Trip A, or Trip B.

But there is one more function that I don't understand.

It changes the odometer to read "Eco." When my Journey moves forward, it says "Eco on." What is Eco on?

 

Thats normal. All the cars and some of the crossover cars do the same thing. As you are driving, the PCM/ECU shut off two or more cylinders. This way you should get fuel mileage.

 

When you are in Eco mode, the display will show you when you are driving in a fuel efficient manner.

 

Good to know, and that may explain why I thought the car was a bit less "peppy" when I acclerated rapidly in Eco mode!

The only really odd thing about this is that I would consider this to be an important enough feature to be mentioned in the manual, which it isn't.