Last night on the way home the oil light came on. The light is question is the yellow oil can with "min" next to it. Once home I checked the level and it was low. I popped to my local Halfords and purchased some castrol edge oil. I topped it up with about 3/4 litre of oil. This was allowed to settle and the level was fine. I decided to give the car a run and too my surprise the light is still on. I've re-checked the oil and its fine but still the light.... what next? The car is a 2008 A3 TDI 170, and it's done 14.5k miles.