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I've had a few cars with very high mileage do this with a dying oil pump, and have found that thick oil can actually help the problem... It will take a little longer to bring pressure up when you start the car, or you can give it a small blip on the throttle to get the pressure up, but the thicker oil hangs up in the engine better so the light doesn't come back on at idle once the pressure is up the first time. I generally use 40W70 for this kind of purpose (yes it's pretty hot here in Adelaide, so you probably don't want to try this in the winter in the US, or if you live in Thredbo or something!)

If it's an engine that you want to keep long term though, just get it checked out and fixed!