I purchased the car in February 2013 with 100k miles on the clock, immaculate and full VW service history. It was last serviced in June 2012, so 15 months ago and 92k miles on the clock. It now has 109k miles on the clock (17k since service) and I've meticulously kept the oil level topped up using Mobil 1 ESP 5W-30......is this long overdue an oil change??