Actually the multi viscosity oil like the 5 w 30 is 5w when cold and 30w when hot....It is designed so that at startup the oil can get through the engine and up to the valves quickly and then build pressure to minimize wear of the top end.....once warm and under pressure the oil moves to the 30 w for normal running. That is why 5w30 is recommended over straight 30 w.
Your high mileage oil also has more zddp (zinc phosphate) that regular oil which in my van shows a higher pressure at startup and a slight increase during cruise.
If you see low pressure from a worn engine some folks move to a 10 or 15 w 40....
If you want to read up on oil......check out bobistheoilguy.com

 

Hello,

I have a 2004 Express Cargo van that i pulled out of storage in 6 years. My van does the same thing. It starts at 40, then idles at 30, and will stay at 40-50 during highway...
I kind of remember the truck having higher pressures, but it seems to run fine.
I would not worry about it...Mytruck takes 6 quarts as i added an engine oil cooler.
I use 5w-30 extended from mobil one...I would not worry about it. I would only worry if it goes under 20 at idle.
I have 91k on my van.....