recently purchased and cub gt1554 with a kohler courage 27 engine. ran it for quite a while,came time to service it. changed the oil and filter, now im dropping a cylinder , seems like a valve sticking or if these are hydraulic lifter engines, a lifter collapsing. comes out of it a bit and runs fine, but seems to be getting more frequent. my first thought is what weight oil this engine calls for and are they that sensitive to viscosity that im possibly collapsing a lifter. of course my local dealer shop is a wealth of info....not