When I do an oil change using the suck it up method I never get over 9L and as the service required warning came up (oil last changed in early June) I checked the oil level - its down a bit. When I read all the posts relating to partial regens it should be up as I do a lot of short journeys (long one to clear DPF every week) and so diesel must be added to the oil thereby increasing its volume. So why does my car do the opposite, no drips on the drive, never any smoke from the exhaust must be something else - but what? Geoff

Could it be burning oil but with the DPF it gets sufficiently filtered that you don’t notice the blue smoke usually associated with this? And possibly only burning oil at higher revs/faster running so much harder to notice a trail of smoke?

Or is oil leaking out but collecting on an under tray or in another cavity so no visible drips on the ground?

Just some theories to explore.

Have a look at the base of your oil filter area. It is common for the oil cooler to leak and there can be a lot of pooled oil there. Then any excess will run down the back of the engine. You would normally also see oil drips hanging from the back of engine undertray blots in a severe case