i have recently purchased a 7th gen honda civic 2005 eagle eye manual transmission. the car is petrol driven. the previous user did not use the oil as per the requirement of the car and poured it randomly. I have the owners manual which says use api grade SG, SH or SJ only. Nowadays, most of the oils are either SM or SN grade. My question to all and especially @xulfiqar bhai is that can i upgrade to SM and SN grade or will it deteriorate my engine. I had gone through some threads which stated that newer grades lack zddp which is essential for some engines. My cars engine is D16w9.