Hi guys - quick question. Had my 03 CLK 55 for two years. Used to go through a litre to 1.5 litre of Mobil 1 0-40 every 2000miles. It's now down to 700 miles before I get a message asking to top up a litre. No blue smoke and no leaks as far as I can see. Any ideas what might be causing this? Thanks in advance