You have to remember that the warranties on cars versus the increased efficiency and quality have led to a balancing act. Did manufacturers pressure API to certify their oils at lower and lower zinc levels because engines are so great now that is not necessary or bad for the engine? No. They did it to weasel their way out of any emissions systems warranty claims knowing that the engines of today can handle piss poor oil and make it through the engine's warranty period. They also did it because the engine will get slightly better mileage with less resistance and make it through the engine's warranty period, which is a CAFE benefit to them with little regard for you. I don't trust manufacturer statements on oil because I know where their allegiance is. Money. Lower API standards also created an industry-wide phenomenon of higher recycling and purchasing of new cars. It's win-win if you build and sell cars. I'm sure the length of time that people hold on to cars is shorter than ever. It's all falling into place.
Meanwhile, I will use the highest quality oils possible that meet the manufacturer's requirements, and switch to the best oil available at 60,001 miles. If my model called for 0W-20, I would invent a novel scheme of lying about what I put into the car and have records showing what they want while putting in what I want. With 5W-20, I don't see the need to have to lie to anyone as long as I can put good quality oil in, but I will never, ever put 0W-20 in my car. People can say whatever they want, the proof is that oils shear to lower viscosities faster when the oil's start-up spec is lower. I've seen it over and over on BITOG.
