My 98 WRX is going in to have the knackered clutch release bearing changed next week. Normally I do everything on the car myself, but removing the gearbox is beyond my powers. Now I'm assuming that it'll want refilling with oil once it's back on, and the rear diff will need the same stuff - 5 litres of 75w90 synthetic should do it AFAIK.

Any recommendations? It's on 118k miles, due for its 120k major service soon, and has been running around 300bhp for the last six months. I use Motul for the engine oil and brake/clutch fluid with no complaints, but noticed that I can get hold of 5 litres of Millers TRX Synth off ebay for £40. How long are the changing intervals for gearbox and diff oil? In other words, can I stick in some good stuff now and leave it in at the 120k service? Surely doing an extra 2k miles between services isn't going to do it much harm.

 

Anyone?