Finally got my truck running today and when I'm in idle the oil is normal and when I'm in drive or reverse no gas pedal the oil is low like it has no pressure at all. If I give it gas in drive or reverse the oil comes back up. Is this just the way it was designed or is the oil pan dirty

 

Are you basing this off the "idiot" dash gauge or a real mechanical gauge?

 

The idiot one lol. Just thought it was weird that if I'm I'm drive and I take my foot off the gas it goes to zero idles fine. Are aftermarket ones hard to install if I can find a good one online

 

Its simply.based off of resistance. It registers anywhere between NormaL when oil psi registers above 7 psi.

I would say you voltage is dropping off as it would normally when at idle or braking to a stop while in drive, causing the fluctuation.

 

If I install a mechanical gauge what would be normal psi range

 

Rule of thumb is 10psi for every 1000rpm.

Cold.psi 40-50 is good.
Hot psi, while cruising 35-50 good
Hot psi @ idle 20 is good

I've ran a trashed 302 with 5psi or lower at idle, with trashed lower and cam bearings. Cold psi was 40.