Hi I have a 311 sprinter that drives as it should with no lack of power etc but has suddenly when idling in traffic for a while letting off big plumes of white smoke when you set back off and gradually getting less and clear when you get to about 50 mph. Fuel economy also seems to of dropped and the oil level has raised about half a litre on the dipstick in about 150 miles .coolant kevels haven't dropped and no warning lights or error codes and drives as normal with no knocks or bangs. Had greenflag called out who said couldn't find anything and to just keep driving and keep an eye on it. I didn't keep driving once it started as also the oil high light was coming on and then off and then at the point where it didn't go off. Engine is clean with no signs of any leaks externally and has 170k on it. The oil has gone a bit thin but has no foamy look or diesel smell and the DPF has been removed and mapped out. It has me confused as drives as it should and no obvious signs of what's going on as I was thinking injector issue but engine sounds when driving and idling as it should.