I just replaced my engine a few months ago because the bearing had worn so much that the rods were knocking. The rod bearing looked like someone took a knife to then and draged the knife across the bearing's. I do run the engine very hard (only once it is fully warmed up) these engines are already prone to head gasket failures, but thats ok. I'm so used to it now the it takes me 4-5 hours to change it Well anyway now that I have another engine in it I don't want to go throught this again. So would it be better that in the summer I do 2 bottles of 20W-50 and 2 10W-30 bottles. At the moment I'm trying quakerstate HM 10W-30 and the engine runs smooth and I get good oil pressure. Better then with penz 5W-30.