I have an RE Interceptor 650, a couple of months old. Just had its first service and the official RE dealer's workshop insisted on putting semi-synthetic oil into it, whereas RE clearly stipulates fully synthetic 10w40 -- CORRECTION: 10w50. My service record makes no mention of the grade used, but I'm guessing 15w50. At the risk of sparking a bunfight, to what extent does this matter? Should I rush out and change to the recommended stuff? I'm in Ireland, so there's lots of humidity but moderate temperatures.