2015 Solera DEF Consumption after 9K miles
I maintain a fuel log and find that I'm using approximately 1 ounce of DEF per gallon of diesel. At 14 MPG, you can figure approximately 1,800 miles per gallon of DEF. This is an estimate and will vary depending on driving conditions and start/stop cycles. Think of it like this "If you can't count heads, count feet and divide by 2 ... you'll be close."
Also, if you maintain your DEF tank and take your MBS for service to a Benz dealer, BE CERTAIN to tell them not to add DEF; annotate their paperwork with your request. Our local Sprinter authorized Benz dealership zinged me for 2 gallons at double the WalMart price; the white powdery residues of which were splashed all over the engine compartment since it only needed about a pint, if that. All this despite my only authorizing "minimal service" of an oil and filter change.