Do car makers recommend oils that help them make their EPA Fleet-weighted Fuel Economy numbers, instead of what's best for the engine?
I took a car that sold around the world, and checked with various oils companies web sites throughtout the world as to what the recommended oils were for that car. In the US the recommended oil was 5W30, second choice was 10W30, in the rest of the world I got numbers like 15W50, 5W40, 5W50. Leads one to wonder - the engines were all made in Japan, and I doubt that the US engine is made to different tolerances than the Australian engine, for example.
I took a car that sold around the world, and checked with various oils companies web sites throughtout the world as to what the recommended oils were for that car. In the US the recommended oil was 5W30, second choice was 10W30, in the rest of the world I got numbers like 15W50, 5W40, 5W50. Leads one to wonder - the engines were all made in Japan, and I doubt that the US engine is made to different tolerances than the Australian engine, for example.