Evening, Have 2006 2.0tdi A3 sportback 107,000m. Normally on the 20,000m service the oil lasts but sometimes at around 18,000 the fuel economy shoots up for one tank and then the engine sounds more rattly then normal and then the oil light comes on. The oil used is the correct oil. Why would this be, does the oil suddenly fail ? Except this year when the car was serviced 5000m, in Feb, but the above pattern just happened, after just the short time. Have had other diesels over the years and have all acted differently. And I do not normally have to keep topping up. There are no leaks and no noticably bad things comming from exhaust, MOT in march. Quite a mix of motorway and country road driving but I dont race or go mad on motorway (Dont hang about though) Should I worry ?