Synthetic oil

I read a post on "bob is the oil guy" forum, by an Australian that ran a large truck fleet, he ran identical trucks, one on mineral oil the other on synthetic.
During the service intervals the valve clearance was checked on both trucks and the one running synthetic never needed adjusting.
He ran this test for 500,000km overall running costs were lower making synthetic the cheaper oil to use even though it was double the price of the mineral oil.