When I fitted my Quaife last June, I checked with Quaife and they said no extra lube necessary as below. I therefore bought the oil they recommended. FWIW, my new diff is absolutely whisper quiet and performs like a dream. Quaife Technical Support page says: "When running a Quaife ATB helical gear limited slip Differential in a standard transaxle gearbox, we recommend that you use whatever your vehicle’s manufacturer recommends. The Quaife ATB Differential does not require any special lubricants. When running Quaife gearbox internals and a Quaife ATB differential – we recommend FuchsTitan SYN5 75W90. For a Quaife ATB differential, running in a rear axle – use a hypoid 90 or 75W90, as above. For those applications that will accept a GL5 or SAE75W90 gear oil, we recommend and sell Silkolene SYN5 75W90 gear oil. We use Silkolene in all our own Quaife racing transmissions"