As someone else has posted about oil usage it jogged my memory and thought that I should mention this in case you're unaware...
With the RS, you need to keep an eye on oil consumption via the dipstick rather than relying on a dashboard light to tell you you're running low, this is because the E85 oil level sensor isn't fitted as it's incompatible with the 3.4S engine. Alpina quote 1L/1000 miles as 'normal' consumption but it can vary quite a bit, Ade's car was drinking 1L/500miles and mine works out at roughly 1L/2500miles in normal use (and a bit more if hooning) - both on Castrol Edge 0W30