I have same problem with my X150 2006 XK 4.2 , I have been advised by the local Jag specialist that it is probably the oil cooler allowing the oil that is getting into the water through the cooler internally as the oil is at a much greater pressure than the water. There are no signs of water contamination on the dipstick and no overheating problems
My problem is that it is no longer available and radiator repair specialists cannot repair this type of cooler ( type that fits between filter and housing), so I will have to search the breakers for a replacement. Anybody got any suggestions?
