You'd have to have a pretty significant buildup of sludge for it to take out a motor, even the smaller 4-cylinder engine.
Realistically, if you have enough sludge building up in your engine (regardless of what the Castrol ads tell you) to destroy the motor, then there's likely to be some other issue causing the motor to fail.
101,000km is only about 60,600 miles, which isnt' all that much, particularly for a Toyota motor. Unless you're filling the motor with the bottom-of-the-barrel gasoline (86 octane or lower, if you can even get it) and used motor oil, you're probably not generating enough internal sludge to have any adverse effect.
I think that "Engine Sludge" is nothing more than the latest automotive buzzword.