Well, I don't know about warranties, I don't pay for them. I've also NEVER lost an engine, even though most of my engines are quite old.
He he, on my 1975 BMW, soon after acquiring it I added some MMO to the gas. Then.......... it must have cleaned out some crud in the carb because a metal tube in the carb actually fell out while driving... it was apparently held in place only by varnish. It was a simple repair.
Some folks look at that and see that MMO is doing what it should. Others look at it and freak out that there was a problem while using the product. Can't please everyone!