QSUD sounds like a marketing ploy. Almost seems like you could leave it in your engine forever.
There are lots of oils available. For no particular reason, I've always stuck with Castrol oils and never had any problems. Castrol is a BP product and is widely available in supermarkets and auto specialist outlets.
Castrol advertises the various improvements to their oils in a fairly low-key manner and don't make outrageous claims. Their Edge synthetics are reasonably priced and seem to work OK. As I've commented before, how would you know that a particular oil was performing well unless you tear down the engine or analyse the oil? Stick to major brands.
The only engine I ever inspected was an Alfa Romeo with 200,000km on the clock and the camshafts and other bits at the top of the engine looked as new. Castrol GTX, changed every 10,000km.