oil consuming can be due to clogged up oil control rings.. which allows engine oil to pass into combustion chamber and burnt.. synthetic oils kept these oil rings clean through out engine life.. using mineral and even semi synthetic oils produces sludge and gunk into tiny holes of oil control rings and oil which should come back down into oil sump, went into upper side and burn.. this is very common when oil not regularly changed.. try engine flush to clean these area and you,ll notice oil consumption issue resolved,, you may need to flush in 2,3 oil changes...