I try to change my engine oil every 4,000kms - give or take 500kms. There is obvious improvement after every oil change. 9,000kms ago I changed oil (Motul 5100 10w50 as usual) and oil filter (K&N 303) as well as change the air filter (K&N). The bike felt much better and reved smoothly. At this point the chain and sprockets were only a couple thousand kms old and well adjusted. I also did an oil change about 4,500kms ago. On the weekend I changed oil and filter (same as per above), I also gave my chain a good clean and wax. I jumped on the bike to run to work this morning and gave the bike a bit of throttle in one of my favorite areas, I quite literally was almost tossed off the back of the bike. Sure I wasn't holding on with deathly tight grip, but I really wasn't expecting the pull it gave. It was revving so much faster and smoother than just a couple of days before. I try to but good (95RON - BP/Mobil) fuel in her all the time. My questions is, should I be concerned with the amount I difference in the bike when I put new oil in her? Considering the oil is less than 5000kms old.