JG-It was good for Harleys, especially when they took the lead out of gas. A capfull in a tank helped lube the valves. I don't think I would use it in a current motor, especially one with FI.
Based on police fleet experience-engines run almost 24/7-idle a lot and also power up a lot-the best thing to do is frequent oil changes. Remembering that oil also serves as a garbage can-a filter can only do so much-so take out the trash on a regular basis. Pull a valve cover on an old engine that has not be serviced regularly and you will find the trash buildup in the valles and rails. We looked in 80-100k engines that had 3,000 oil changes and they were perfectly clean.
Unless you have an extreme heat operation-the cost of sythetic oil in an engine would be better spent with a good straight oil and more frequent changes.