Oil Light turns on, but oil level is fine?

I have an older Subaru Outback. I know the head gaskets are failing but the repair would cost more than the car is worth so I plan to just drive it until it dies and then scrap it and move on. The "service engine soon" light comes on a lot, the code is related to an oxygen sensor in the exhaust, but the... show more I have an older Subaru Outback. I know the head gaskets are failing but the repair would cost more than the car is worth so I plan to just drive it until it dies and then scrap it and move on.

The "service engine soon" light comes on a lot, the code is related to an oxygen sensor in the exhaust, but the root cause of the issue is the fact that the car burns oil or coolant or whatever.

Lately the oil light has been coming on for brief periods of time. It comes on when you first start the car and all the dash lights turn on, but when the other lights turn off the oil light will stay on a few seconds longer, sometimes for 30-60 seconds. then it turns off.

I've checked the oil many times and the oil level is good. Its been less than 2,000 miles since my last oil change and the oil doesn't look black or burned, so its not due to be changed.

I'm just wondering what could be causing the oil light? Is it possible for the leaking gaskets to allow coolant into the oil? Like maybe its burning or leaking oil but the level looks right because coolant seeps in? Could there be a problem with the oil filter, like maybe its clogged or something? The coolant does run low over time, I top it off every few months but its not bad.

I'm planning to take the car on a (somewhat) long trip - about 300 miles round trip next weekend so if there's something simple & cheap I can do before then like replacing the filter I'm all ears.

Thanks.
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