You can track it as a note. That will cover cost and odometer reading. It will add the cost to the per mile figure. I think you'll have to track the volume per mile yourself if that's the goal.
I just bought a new 2017 Dodge RAM 2500 (w/DEF) replace my 2008 Dodge RAM 3500 (non-DEF). I need to track cost per mile and adding this to the fill up page would be a nice feature that I requested. In the meantime, I Have created a separate vehicle call Def-Dodge and I enter only my DEF information there (mileage, gallons, cost)
To see cost per mile I just go to statistics, search and select both dodge vehicles and the accurate cost per mile will show.
That works for you, but obviously it's going to screw the averages for every other vehicle of the same type. That almost 300 MPG will be added to all the Dodge Rams of that type.
On the Dashboard page, just under the add a fuel up button, is a button to add a note.
You use note to track DEF use and other items. It includes cost and odometer reading.
Create another vehicle called DEF, type = Other, Year, then the following required fields allow you to enter custom names. I entered "None" for required fields. It won't mess up any vehicle's numbers. Works for me.