Originally Posted by Nomad Willy
I don't understand the resistance to mono 40W. As long as one's engine cranks smartly at startup.
Oil can be very sluggish and thick at startup, and it is imperative that the cylinder walls receive adequate oil to cool them. When oil pours like syrup it can not wash the cylinder walls and remove the combustion heat.
That is why they say wear happens more at startup than at any other time for a motor. Oil starvation. I have seen lots of dirt bikes suffer from the piston seizing up because they never let the oil warm before racing.
That said, I have a good friend thats been grinding cams for better than 40 years and to this day he swears that his empirical evidence shows that a straight weight diesel (rotella) will protect the valve train much better than a multi grade.
I run rotella synthetic in everything I can except the genny. It gets rotella 40w, easily obtained from oriellys. Its so much quieter running with it. To me the quieter running agrees with a straight wt oil being better for valve trains. At least for diesels.