yes of course a turbo gdi engine will coke the oil unless that conventional is changed sooner than 3k routinely to not get varnish. But people think that in general its impossible to have a clean looking engine without any varnish with conventional at 3-5k intervals even in a port injected na engine. He said nothing but Pennzoil conventional so i take it as never having even a flush or additives also. Which i personally wouldn't do in a well maintained engine since new unless its known for cleanliness issues.It depends on the engine design, also many "conventional" oils now have synthetic in them to help meet spec.