Originally Posted by kam327
Yes I understand that's one side of the argument. I tend to go with the other side that believes the oil film coating the engine internals since the last run is enough to protect everything during the split second the oil first goes through the filter and into the engine.
Plus I don't like to send unfiltered oil straight out of the bottle directly onto my bearings and pistons.
I have heard some horror stories concerning oil straight from the can but, when I worked in hydraulics we filtered the oil in the drum for at least two days before putting it into storage. The filter cart ran a 3 micron absolute filter and they hadn't changed it in 5 years, when we decided to do so it looked good as new. We were using Mobil DTE24 so maybe premium manufacturers do a better job.
The instructions for the Amsoil kit says to prefill the filters but I assume they trust their own oil. I do agree with you, evidence absent to the contrary that the existing oil film in the engine should be sufficient to protect the engine during initial startup in an already lubed engine.