Your right Jade, the rings in the GenIII's weren't the best and many owners had alot of problems (rebuilds and even new engines to resolve). 5w-30 is what Castrol recommends for that engine and to be honest 4 GenIII's cant be wrong. None of these vehicles ever used a drop of oil and 3 of the 4 covered over 80,000km's before sold. The 5w-30 oil was used from the first 1000km service right through to the end of ownership with no hassles. That has to say something right? ← Hate to break this to you but our cars don't have genIII's :P :P :D