I think modern oils are really aimed at modern engines, especially where you have turbos spinning at high speeds. Semi-synthetic fne for LS, (unless you want to drive every where in 1st, and keep the revs as high as possible).
Fully synthetics are designed not to break the oil (chains of atoms) at 7000rpm and above for sustained periods. Mineral oils cannot sustain this kind of abuse for long.
My LS (202,000miles), uses next to no oil between 10k services, and where I have topped it up, usually less than 0.5 litre just used 10-40W (which is what I use on my wifes X-type - which eats oil for a living - only done 130,000). I have never observed what 'smoke' comes out of exhaust on cold start, though I do check from time to time for water (only because I ignored water on my Omega - which was gasket going. I was being stupid and thought coolant needed replacing as I had a leaky hose, where as it runs out the car was p*ssing water out the back). Still if the Omega had not blown, I may never have got to own a LS 13 years ago.
I must confess I have never asked what my garage uses for services, other than I know it is not fully synthetic.