C30 Engine : C30 Oil Consumption

[TomW90]

Hi, I bought a C30 R-Design Lux (petrol) in September, 83k miles. I seem to have an oil problem. So far it's got through 4 litres over the course of 3000 miles. That seems very excessive to me, but I don't know if it's normal or not. The local garage can't find any leaks, and I haven't noticed any smoke, smells or lack of performance. I've done a youtube PCV "glove" test, the glove didn't inflate or get sucked in, it just sort of mildly blew in and out rapidly, so I don't know what that means. It's under extended warranty, but there's a claim limit, so before I start going down that rabbit hole, are there common problems with this model to point to, and are they reasonable to fix?

Any advice much appreciated.