Lucas Response To Zinc Additive

Bottom line it's internal friction we're talking about here.
You will never go wrong with a fully synthetic oil like amsoil,royal purple, mobil one etc.
Break your engine in with standard mineral oil and an additive like e.o.s. for example, and then switch to synthetic. It's well worth the insurance and the cost isn't that bad if you factor in the wiped cam lobes and replaced parts you face.
Check it out, synthetics work.