Low Oil Pressure???

It’s a 2018
It does use some oil maybe half gallon every few weeks.
My oil gauge is like yours which for the life of me I can’t figure out what the lil marks would be in between I’m assuming 0 and 25 it doesn’t divide equally? (See pic)
I only have a digital boost gauge and oil temp which I’ve been monitoring since yesterday when this started. (Definitely need gauges) oil has been staying close in line with engine temp peaking at around 221 at most. Boost seems to be normal.

 

Today it done good all day.
I went and unloaded dead headed couple hours reloaded and about an hour and a half in it started slowly dropping below 50 then hovered around 40 and once I hit the interstate it dropped down around 30 and I shut it down for a bit. Then fired it up and made it to rest stop.
I also had to add more coolant today almost a gallon.
I pressure tested over the weekend fixed one small leak re pressure tested and held solid.
Reverse pressure tested and let engine run 5 mins and no pressure built in coolant system.

 

I just fired it up after letting it cool and it took a good 15 sec for oil gauge to move up. To the point the engine started struggling and as I was grabbing the key to #### off oil pressure came up and it smoothed out.
I think I got a few different problems and nothing easily fixed.
I bought a full warranty through FL rekon it’s time to see how it works.

 

That’s low idle on warm engine. Cold low idle it’s much higher.

What are your normal readings idle, driving etc so I have a comparison of where it should be.

 

Well turns out I had a cracked liner, had an in frame done.
Picked it up last night got half way home and it threw an injector code.
Dropped it back off today so they can replace the faulty new injector that was put in.
Hopefully they’ll be done by Friday and I can get back to work after almost 4 weeks down.