Intermittent oil pressure/lack of oil pressure

Glad you got it back on the road. 5w30 should be fine.

I would say that it was not a filter failure. When that one happens the lifters all start to rattle, and you pretty much crap your pants.

If however this was an older engine with 40k of conventional oil use, you may have had a filter element full of junk the synthetic helped to dislodge. That means that at idle, the oil had to push past the bypass valve, losing as much as 10 psi in the process... So 15 psi looks like 5 on the gauge.

I agree that 30 weight oil is a little light for an older engine with some miles on it. You may well see "low" oil pressure at idle. Not an issue if the pressure swings right up off idle.

If you are staying with Mobil 1, they make both 5w40 & 15w50 oils. All the first number means is how it pumps when cold. Since you live in a mild climate, any of them are ok. If you lived farther north, the 0w40 might be a better choice for cold mornings.

The lower the cold viscosity, the less stress it puts on that oil pump drive on a cold start. Easily the weakest part of the LA engine as far as I am concerned. A cold start with a sump full of straight 50 oil causes the pump to work very hard, and can cause pressures to rise above the relief valve setting. If you have a 60 psi relief setting, and you see pressures above that on a cold start you should go to thinner oil.

B.

Edited to add:

Please thank your wife for her service. We really do appreciate what she does for this country.
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