Does any of the engine manufacture have a limit on wear metals? The reason I'm asking is: I have a CAT C-15 and my UOA @500 hours had Fe @ 96 PPM and the 1000 hour went to 196PPM. The lab I am using flagged the oil at the 500 hours saying 96 is too high. They are going by average of what they see (which is 20PPM @ 265 hours). The engine has 2500 hours and I am using AMSOIL Signature Series 5-30 (DHD)