You are comparing 2 different oils running in 2 different cars??
Mobil 1 0W40 is probably their best M1 range they offer here in Aust. It meets MB 229.5, where it is used in cars who's OCIs of 30,000ks+ are the norm. For it to go 'off' in under 5000km just by looking at it is just an assumption, especially with no oil analysis results. smile.gif Perhaps the thinness of the 0W40 promoted more oil consumption, same with the Castrol R 5W30.
I suggest you try comparing the OEM certs between Motul 8100 and M1 0W40 and you'll see which is superior.
Sir-D, Helix Ultra will do a 10,000km OCI comfortably on a stock motor, providing its in good condition.