Oil pressure when cold.

An update from this morning.
Used the magnetic heater all night on the oil pan.
Started up this morning, the temp was 1 degree, fired right up, oil pressure slowly went to about 30 psi.
Let the truck warm up for about 10 minutes, oil pressure was at about normal 20 psi for the motor temp, drove the truck to work.

After work started the truck up, it was 8 deg out, same crap low oil pressure.
I guess 10w-40 is way to heavy for temps below 10 degrees.

here is the heater I used.

http://www.amazon.com/gp/product/B000BOABS6/?tag=joeychgo-20