@Jacko i was actually about to make a mention on something about exactly this, I used to run edge 5w40, by 3500km i chewed through 1l, so 1l top up, and then in 2000km that 1l was chewed up, top up -> then lucky if i got another 1000km out of it before top up.
I switched to Penrite HPR, it's been 5400km since the fill and have just chewed through my first litre, which is substantially better than 3500km on the edge, hard to say 100% for sure right now, but if i make it to my 7,000km oil interval without having to top up, this pretty much would suggest that Castrol Edge oil integrity breaks down quicker than penrite HPR in a substantial way.
No real leaks either to add to usage, sump is relatively dry, oil cooler gasket is dry, block is dry,. Just the od "seepage" here and there in common places.