I agree. An appropriately serviced engine will usually outlive the rest of the car, so what's the point in paying for stuff that's not necessary? Take the oil filler cap off and have a look down the hole with a torch. Not all engines will allow you to see much down there, but if it all looks like oily metal, it's fine. If it looks like black sludge (and I mean something with a consistency like toothpaste, rather than liquid oil!) then there might be some merit in using it. I've just scrapped my last petrol car at 250,000 miles and I could have almost eaten my dinner out of the cam covers!