Stopped at my local Toyota dealership yesterday to pick up an oil filter for my first 5000 mile service. I inquired at the service department as to what weight oil they use in the TCH. They said that either 10w30 or 5w30 was to be used as per Toyota's specs. I asked if they ever heard of using 0w20 and they responded by saying " in what...a sewing machine?" I am just wondering if a different viscosity oil is used other than what the manufacturer recommends, could it void the warranty if there is a mechanical problem of some sort? What is the actual benefit of using 0w20 compared to a fully synthetic 5w30?