I have used the castrol 5/30 magnatec oil badged as suitible for new ford engines. My local ford dealer also uses this oil when servicing apparently. Not sure if it is fully synthetic or semi synthetic. The local dealer did not recommend using fully synthetic as there had been previous problems with sticking valves on the duratec engine using fully synthetic oils. Having read a previous thread on 100ps v 115 ps engines and the attached detail on the development of the 115ps engine I would be very wary of changing from the recommended lubricant. It has electronic thermostat and integrated water