More likely than rings is that it needs valve stem seals. The oil is probably leaking in from above down the valve rather than past the rings. My 300E needed this....it was fouling all the plugs with only 133k on the engine, after new stem seals it uses 0 oil between 4,000 mile changes. Amazing difference.

Also, if that 420 has not had the timing chain and guides replaced, it needs it BAD!

And why junk the whole car because the engine needs some normal repairs/maintenance? That is the typical wasteful mentality of the USA......

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)