The AWD Q50 has 4 additional mechanical fluids other than the engine oil that need attention. The rear differential (same as only RWD Q50) as well as Front differential oil, transfer case and transmission fluid.
Historically, I have found that the differential fluids have usually got a specific mileage at which they must be changes, however for the Q50, the only recommended maintenance is to Inspect the fluid every 10,000 miles or 12 months, unless towing a trailer, or driving in rough conditions in which case it is recommended to change every 24 months of 20,000 miles.
