Just a quick update: I have discovered oil in the cooling system so took it to the garage. They cant determine the problem other than an oil cooler fault, or Head Gasket/engine block problem which requires a process of elimination to be able to determine the problem. Consequently I had the cooler changed as the less expensive 'problem', but it has returned after a few days/500Kms or so - suggesting problem might be with head gasket (although no overheating). Hopefully not as it costs about AED 20K to fix. Its currently at the Garage who think the oil is old - That's a good sign as it might just mean that it wasn't properly flushed through after the oil cooler was installed. Whilst discussing this with various Porsche specialists is seems that this is a regular problem, and something to look out for when buying a 2nd hand Cayenne; I am told it has been known for a seller to replace the Oil Cooler and then sell the car just afterward as usually the problem does not make itself known for a few days/weeks. If there is oil in the cooling system, after a while you can observe the coolant looking like a 'chocolate milkshake'. I would suggest when buying if this problem has occurred and asking the seller directly if the Oil Cooler has been changed - and if you are having the vehicle inspected to ask them to check if there is evidence of a replaced Oil Cooler.