oil pressure question

ok i noticed this about 2 weeks or so ago...it's been pretty cold here too. ever morning when i start the car up, oil pressure is a little above 75psi....after a minute or so, the oil pressure drops to 50, then right back to 75, then goes below 50 then back to 75...the needle just keeps going back and forth until the car is warmed up, then it doesn't do it...this is the first oil change where i have used Lucas Oil Treatment. i've been running this 5w - 30 Castrol Full Synthetic w/ Lucas for about 3,000miles now and there is plenty of oil left, according to the dipstick...also, i've noticed since this previous oil change, my overall oil pressure has rised a tad....normally in 5th gear at 80mph or so it'd be at about 75psi....now i'm hitting 75psi in 5th at around 70mph...is any of this normal?

thanks for any help

when I ran lucas oil stabilizer it was too thick for my pump to pump it up to the top of the head so my cams locked up and shit, runing my 2nd motor while using that stuff. i don't necessarily like it.