340 oil presure drop

I think cold oil, creates higher pressure, then looses some as engine warms up. All my vehicles with gauges does this senario. They claim, 5w when cold/30w when hot? I`m no lubricant engineer, but does it really work as claimed? Anyhow as long as you dont have a significate drop in pressure I would`nt worry. But If yours goes from 60 to 20 or 10, I`d be suspicous. I have a ferd 390 w high volume pump that near burys to 100lb + then drops to 60-50 after warming :-D