 Purchased a 1998 1.8T passat with a blown engine for $1000 and I rebuilt the engine over the summer.  There is a lot of chatter about oil sludge destroying these engines, this is completely false! Oil comes through a metal tube around the back of the engine over the catalytic converter, exhaust manifold and through the turbo charger.  Non-synthetic oil cokes (forms hard particles called turbo-turds)inside all of these components.  Eventually enough of this coked oil breaks free, clogs the oil sump screen and oil starvation occurs.  This is what causes the vast majority of 1.8T engines to fail.  Either VW engineers are complete idiots or this is an engine designed to fail.