I've been involved in way to many oil wars in the last few years. Most start on the Harley boards, but the old car version gets even more intense in some "places". Bottom line on the Harley's (new engines) is quality oil changed enough to keep it clean. I'm good with that, have my own choices and intervals and they work and I'm good with it.
Old cars is a bit different. Had Mobil 10-30 Special in the 63 for years(30), untill that stuff changed and lost the zinc. Went to 10-40 Valvoline Racing 'cause it has the zinc we need. Now I find out the 10-40 will burn down the engine and melt my fenders. But 20-50 Diesel is alright,, ( I never was on that bandwagon), and 20 -50 synthetic is great even though the other multi vis oils are from the devil...... along with the fact that it will leak out of every gasket and maybe even the pours of the castings. And of course the ZDDP additive doesn't mix with the oil either, so now I have to come up with new oil before spring. Crap. Why doesn't somebody make oil named "Old Damn Car Oil" and take the heat off ????
Seriously, just about all the arguments make sense in one way or another. My old engine WILL smoke on start up for awhile after the winter storage. Is there actually a Dyno (non synthetic) oil in a straight weight that has the zinc out there yet ? Are the multi vis oils really that bad ? Guess a 30 weight with zinc would get my money.