By accident I have topped up the oil in my TDi (1998 110hp) with cheap 5/30 instead of quality 10/40. It was registering on the minimum now it's showing near maximum. I simply picked the wrong bottle up - same colour and design!!! The car is due a service including oil and filter change in early June. Do I need to worry? Is there anything I can add in as an additive if so? Stu.