I'm using semi-synthetic 10/40w motorcycle engine oil, I always use a genuine Honda oil filter, as for the spark plugs I'm using SplitFire at the moment, I don't know if they are the best but I fancied giving them a try
I got some of those Iridium ones off e bay and I cant say for sure but i felt it had a bit more snap to it after fitting but then again this may have felt the same with any new plugs ? I also cleaned the air filter at the same time so who knows.
But i did find a bit of an improvement in performance