Large oil sumps (7-8L) mean twice as long oil drain intervals compared to small (3.7-4.0L). It was all done for the fleet buyer who basically wanted a) minimal servicing costs and b) resale on the used market to be close to what they bought at on the subsidised fleet bulk buyer market.
Nothing to stop someone using a fleet oil from a motor factor like Comma, it will be a fair bit less. Note generic oil filters often have different bypass oil pressure compared to OEM. This can raise its head during cold starts etc.
Check your air filter if getting a bit forgetful, the rubber seal DOES break down with age and go through the engine & lodge in the cat. I know this because of the smell of burning rubber once and it was not my tyres... had completely forgotten... must have been 8yrs rather than the suggested 2yrs. Mileage wise it was right, but age wise things do deteriorate. Likewise coolant level is easy to "drift off to the back burner" when something somewhere gets a tiny bit leaky (crack in a plastic fitting which only propogates over years and only opens at certain temperatures).
Modern diesels are very hard on their oil, the particulate buildup is severe and multiple short trips or poor monitoring of oil level can result in very big bills. Things are also not well made, intercoolers are the thinnest aluminium they could get to come out of the factory without imploding on impact with a neutrino.