Don't run the engine even a little bit with too much
oil. If the crank gets into the
oil it will foam it up.
Sometimes going to a thinner
oil will increase the gauge pressure because the pressure sensor is on the engine side of the cooler and filter. The original thicker oil did not flow as well and much of it went out the by-pass. The new thinner oil is able to flow through both the filter and cooler and thus provide higher pressure to the engine
Just my $0.02
Bob