That is true. Unless you want to run it for 250,000 miles and tear down the engine and measure clearances and wear. Fortunately though, others have done this, and the results are readily available on Youtube. Or even better, there are very stringent tests Euro oils have to pass, so you could just trust that those oils passing those tests will perform well.That also means that there is no easy way we can test the expensive oil's big claims. I'm sticking to the cheap one