I have a 3.0 V6 CDTI Estate. Covered 15'000 since its last service and yesterday the oil light came on. I pulled over to check and the oil level was just on the dipstick. I know the oil was done on the last service but to use all the oil in 15'000 miles or 7 months seems excessive. There is no sign of a leak on the engine and no drips on my drive. I cannot see any smoke when driving or when revving it on the drive. Most of my driving is at motorway speeds 75-80mph using cruise control at about 2000 revs. Anyone got any ideas what the problem may be?