Oil pressure problem?

thats the way mines been since I first put the 360 in my Dart 4 years ago... pressure around 60 when fired cold... once hot, especially idleing in traffic, its around 10 or so, until the light turns green and im back on the gas... then it comes back up.. my friends told me that was normal so I have never worried about it.. whether they're right or not I dont know, but I havent had any motor trouble in 4 years..