Water-thin synthetic oils like 5W-30, etc. have no business being in an engine with oil clearances designed for straight 30 weight.
Jerry, I don't think you're understanding the multi-weight designations. 5W-30 oil (whether synthetic or conventional) has the SAME viscosity as straight 30 weight when it really counts, when the engine is HOT. It's only the same as 5 weight oil when temperatures are extremely cold and only assists in starting in really cold winter temps. That being said, 5W-30 is likely a bit too low a winter viscosity for most stovebolt users.
