amsoil

I have an 2008 KLR. I have noticed the oil seems a bit low (although it's hard to see if the bike it truly level). The guy I bought it from used the "top of the line" amsoil 10w-40 in it. 1) What is the best type of engine oil I should run in the KLR? 2) Is the 685 Piston Kit the only fix for...