Originally Posted By: old1
On my classic cars that sit for long periods between uses quite often, does conventional or synthetic leave a longer lasting film for restarting. Or doesn't it matter in the least.
In classic cars I would use an oil with a high x in xW-y, such as 10W-, 15W-, or 20W-, meaning a thick base oil, and a high moly and ZDDP content. This assures best wear protection in classic cars where valvetrain stresses can be unforgiving. Conventional vs. synthetic is probably secondary.