Hi I have a Air Arms s510, which is a 177 and I use JSB Exact 4.52, but all in all it is up to each person what they feel at ease with. I had a Walther .22 break barrel prior to this s510 and there is no comparison, the Air Arms to a much nicer gun, a little like getting out of an old austin mini and getting into a new Jaguar, if you get what I am saying.
I have purchased through ebay and I believe that there are so many copies of everything on there that you do not really know if what they are selling is what is in the tin.