Low oil pressure on 1994 Honda Passport

I just bought a 94 honda passport, and took it to jiffy lube to have oil changed. I'm not sure if it was before or after but the oil pressure runs at nearly 0 at idle and about 35 while driving.. I then proceeded to do what I should have done and changed the oil myself, with some heavier oil (10w40). Since then the oil pressure is about 5 lbs more.
One important note: the oil pressure is nearly perfect before the vehicle warms up. Then once the normal temperature is reached, the oil pressure drops. (which is why I started by using a heavier oil.)

Asked by for the 1994 Honda Passport
The oil grade is important your right. Maybe your oil gauge is not working properly or possible oil pump, clogged filter or strainer, or regulator valve problems.