Breathing fatty gooo . . .!

[mike st gilles]

As has been said this is unusual with a diesel as they normally work at higher (relative) temps than petrols. The cause is that the engine as it heats up and subsequently cools down produces lots of nasty water and other odds and sods. It is only when the temperature of the oil exceeds the boiling point of the water that is now contained in the oil that it will allow it to 'boil' off.
If the car is only used for short journeys, it will boil off this stuff but it will be contained in the breather system and will if not 'blown' out on a 'longer' trip then proceed to condense on anything that is cooler in relative terms; ie. breather pipes, oil cap and the like.
The fact that the car has been standing for a fair time only serves to confirm the above...........I bought a CX off of Ebay that had been standing for a fair time and the first diagnosis when I looked at the dipstick and oil cap was that the H/gasket had gone ......... drove it home 140 miles and reasoned that the AA could rescue me if it was that .........drove home with no probs getting braver all the time and by the time I hit the M40 I was doing the usual motorway limit.
Got home and checked the oil in the morning and the mayo had all gone in the main just a bit left on the oil cap; the run had 'boiled' the water and goo away...............still needed to clean out the breathers and pipes and oil and filter change etc after but the problem never reappeared.