Yesterday went on a small trip. I had drove about 200 miles and my oil preassure was holding about 20 psi. For the past two years in between oil changes it drops from 40 to about 20 and thats where it stays while i'm driving. Well yesterday i noticed during the 200 mile drive it was fluctuating between 20-25. About 10 miles before reaching my destination it dropped to about 15 psi. Next thing i know it's about 10 so i stop and pull over. I let it idle for just a minute and it dropped to 0 and the low oil preassure light pops on so i turn it off real quik. I wait for a while start it back up and it still fluctuating bad but don't drop below 20. I have put about another 150 miles on since and hasn't dropped below 20 but i know i have a problem. What could it be? When i started loosing preassure couple years ago i got a little worried but it has never acted like this.