The problem with "fill rate" is that it can be manipulated based on the way you receipt parts into your inventory system. Your particular mix of wholesale, retail, and warranty can make a number like that better or worse and just the opposite for other dealerships.
The reality in our business is that we manage a "reactive retail" inventory with a large proliferation of part numbers. How we set our phase-in and phase-out criteria will make a huge difference in inventory performance. Setting your phase-in criteria too tough, will make your fill rate suffer and too loosely, will create excess inventory. Fulfilling true demand, no matter where it comes from, should be the objective of any changes you make to these settings.
We suggest that a 90 to 95 percent fill rate would be a long-term goal for high off-the-shelf levels of service to your customers.