Hi.I have just done an oil change on my disco 300tdi and put in 5.8 litres of oil as indicated in my hand book.However when I dip for the level, the dipstick indicated nothing.I have done the usual ie turned the engine over,switched off,left it for 30 mins. to settle,dipped again and nothing.Please advise.Many thanks in advance.Ps there are no oil leakes and the oil light goes out on start up.