Hi, over the past year I have topped up my engine oil on three occasions, about 5 litres in total. The car is under warranty so I have taken it to VW, they are saying they have checked it and cant find no fault and that if I want further investigation its going to cost me £67.15 as they are not sure it is a warranty issue. I am not sure what exactly to do next as engine oil shouldnt just disappear... She said one factor could be the high mileage that I am doing- about 15-20k a year. Any advice on this would be greatly appreciated. Thanks