Why is my oil pressure warning light flashing after a long trip?

I have a mitsubishi 3000gt '92 and I just change the oil(I put in 5w30). The car doesn't have any leaks and the engine doesn't feel like lost its power.Why is my oil pressure warning light flashing after a long trip?
The viscosity of the oil you've used is too light. After a run, the oils thins with the heat and is harder of your oil pump to pickup and pump. With a 15 year old car this happens, and if this continues it will stuff the motor. To fix, replace the oil with a heavier grade such as 10w40 or 15w50.Why is my oil pressure warning light flashing after a long trip?
Your oil sensor is probably the prob. The wire connect to the sensor, the wire its self, My guess is after many miles heat is doing a no. on your wireing. Old wireing builds up resistance, so have a complete checkup, bumper to bumper, 92 its time!! Or you could do what I do, I d put in a S. W. guage. I hate idiot lights!!
the oil pressure switch would be the first thing to replace or called the oil sending unit....
your oil may be to thin for your area or for its age. older engines need a little thicker oil. BUT, the best thing is to have your mechanic check it out for you.
';Long Trip'; How many miles on the engine? might need to go to a little heavier oil ';Havoline 15W-40 or Coastal Hi-Mileage';. Oil pump could be getting weak after long trips. Personally I'd go with the heavier oil.
your oil pump may be going bad, is the oil low? if so than you are burning oil.
it can due to a bad quality engine oil because by getting hot it los the tickness,if you have not change your oil filter resently do it this time when you change oil.or a lazy oil pump.check that yor ingine temp. does not get to high,that could in some cars problem with oil pressure.good luck