As warranty of my punto is now expired and no service center near my home, i am planning to visit FNG and change engine and other transmission oils this time. Engine oil recommended by manufacturer is Selenia K which i guess is semi synthetic oil. I am planning to put mineral oil as my running is very less(<4k/year). Whether changing from semi synthetic to mineral oil is advisable or not. Furthermore Fiat recommend 5w-40 grade engine oil but i am not able to find mineral oil in that grade. Changing this to 15w40 is advisable?