996, 986 Boxter: Pretty much well-sorted sports cars, but with the fatal IMS (intermediate shaft) flaw. The angular contact ball bearing that locates the intermediate shaft between the cam driven sprocket and the camshaft can wear significantly, bind, and break, causing the crankshaft and camshaft to come out of sync in a valve bender/ piston smasher/ conrod flailer event (on that cyl bank). IMO it's poorly thought out design detail in an otherwise clever and refined engine, and sadly, there is no reliable alternative than replacing those bearings to reset the self-destruct clock.
A friend of mine with an '01 Boxter has made a point to me that he will never buy another Porsche due to the way they (one of the most respected dealerships on the East Coast) passed off this fault as "a normal, typical high performance engine design, where catastrophic failures come with the territory, even at fairly low mileage." If you read the Rennsport forums you will see several years worth of disappointed owners ready to unload their Boxters & 996's, and Porsche North America now offering an out-of-court settlement to the class action lawsuit that pro-rates out of pocket rebuild repair expenses based on the age & mileage of the already affected cars (but accepts no responsibility for the poor design being the source of the problem).
If I were you 855R, I would ask the previous owner for service records on the intermediate shafts, or have them checked out ASAP. At least there is a warning for those who pay attention: most of those which are borderline make noise from the bearings for some time before they break.
And what oil to use? The one which lubricates caged ball bearings the best! But anecdotal evidence seems to show no correlation between type of oil or filter used, OCI frequency, driving habits, and IMS failure. Sorry to rain on your parade, this tempest has been brewing for 5+ years now - you should have done your homework, because even Porsche can make lemons.
