I own a 2010 E-3504-Matic with P1 & P2 Options. I had the car into the Dealership for the 70,000 mile warranty Maintenance Service. Upon driving home I went to my Multi function Display to see if the Service display was Reset n the ASSYST-PLUS. I noticed the display had days to Service, before it had actual Mileage to Service! I read somewhere to reset the Multifunction Display back to Factory I held in the brake pedal in for 10 seconds while pushing start button once, after waiting ten seconds release brake pedal and hit start button once. Wait 30 seconds and start car. Service days should be mileage now? Well, I can't get it back to Mileage...... I want the mileage for I change oil filters every 5,000 miles. Synthetic Oil works best with New Filters, traps more dirt and any metal particles in oil! How Do I go back to the Display Showing Mileage?...............

There is no setting to change that as far as I know. It is based on how many miles you drive. If the system calculates that you should reach 10k before 1 year from reset, it displays mileage until due. If you don't drive much (like me), it displays days until next service interval. Don't worry it is keeping track of miles regardless and if you keep driving more, it will show up. In the meantime, just make a note of the odometer mileage from the last service invoice to track it yourself.

I reset the second mileage minder at every oil change.

thats what i was thinking too , that it would show miles as you drive
but idk if thats true or not

I have seen it change from time to miles and back. After my last service, I wasn't driving much so it showed days until next service. Then after a road trip it showed miles until, but then after a few weeks of low mileage it switched back to days.

on my car it seems to alternate between days and miles every few weeks.