Yes Trajan the tendancy now is to lease vehicles to people who care not about upkeep. Like I have mentioned only a boob would recommend one type of oil for all.
If the vehicle requires synthetic, it is one thing, but only the ignorant would make a blanket statement.
Sludge is an issue for those lonely middle age men, desperately looking for attention on internet forums.
Haven't seen sludge nor has anybody I know.