Originally Posted by painted jester
Even when left for a while the older oils with zink provided a layer of protection because the zinc is a high pressure lubricant that adheres to the metals like crank and bearing material its too bad its been taken out of most oils now! But the new lubricant additives must give good protection (except for the cam).
Yes all true but bearings are made out of a lot more metals than lead and tin. Usally they are zinc coated i was always taught not to even touch it or the caoting will react with the acids in your hands. It is also there for the rest of the life of the crank over years of wear these metals are taken off and that is when the crak begins to fail.
If you never had metal to metal crank contact you would never need to replace the bearings. They would never go bad with just oil touching them. But sadly that is not true they touch on start up and other times in an engines life when oil to that one bearing gets low or over powered and squished out this usally results in spun bearing.
I didnt think new bearings were made with lead in years since its not enviro freindly. When you pay extra for nice high performance bearings you are buying coatings, and they are alot more than flat metal that is the easy part.