The sludging problem occured in regular Toyota engines...the kind you see in Camry's. It is my understanding that Toyota more or less caved in to a lot of pressure and never really admitted anything was wrong with the engines. The settlement applied to those with failed engines who could prove they changed their oil at least annually. A low threshold for sure.

My own opinion is that Toyota purposely designed an engine that ran somewhat hot, for emissions purposes. It wouldn't fail if owners adhered to the prescribed oil schedule. My guess is they didn't leave enough margin to account account for the sloppy maintenance habits of many car owners.

I've never had a sludging problem...heck my cars after 200k miles show no sludge in the camshaft cover. But I change the oil at 3,000 to 3,500 miles.

Volvo, like Toyota and all other car makers play a numbers game with maintenance. They know consumers watch the annual maintenance cost number computed by one of those consumer mags, so they keep required maintenance at a minumum to hold that number down.