FWIW, thinner
oil (i.e. 30 weight) will drop your
oil pressures quite a bit if you are used to running a heavier
oil (i.e. straight 50 weight or 20w-50 multi-grade). Your cold pressures will be the same, but the warm side will make you go "Hmmmmm....". Also remember that with multi-grades, the oil is designed to act like two oils in one. For 20w-50, it will act like a 20w when cold (thinner viscosity) but settle to a 50w (i.e. more heat protection) when hot.
You can get dizzy and get a WIDE variety of opinions when talking oil. It's almost as bad as going with the wife to buy carpet.
-Dean