Unfortunately it was a simple matter of the air filter not sealing properly. I just used a cheap paper filter for a service and only found out later it wasn’t sitting properly. I was doing a lot of driving on country dirt roads at the time and it had ingested a lot of dust which scored two cylinders and led to reduced compression and very high oil usage . I should’ve been checking more often than I did, but it ran out quite quickly. I’ve never missed a service, but from now on I’ll be doing shorter service intervals and checking over everything more often. Also be using a proper oiled K&N air filter from now on.