OK, my '82 has a mechanical oil pressure guage, for whatever reason. It reads about 50psi when it's cold at 2000rpm, and 30-40psi at idle (750rpm or so). After driving it for a while it drops down to 40psi at 2000rpm and like 10psi at idle. Is this REALLY the oil pressure dropping, or is it just something with mechanical guages? I've heard that the mechanical oil pressure guages rear a lower pressure once they heat up, because of the air in the tube. BUT, that's from my brother and he's wrong a LOT, so I'm making sure. Help?

 

well oil pressure should drop as engine temp raises and you get to normal operating temp.You can always get a mechanical pressure gauge and hook it up to see what it really is, im pretty sure after 27 years the stock gauge is not going to be accurate

 

Well, that's the problem actually. The stock guage isn't hooked up at all, the last owners had a mechanical one put in (along with a volt meter and temp guage), so I'm just worried cuz if the mechanical guages ARE accurate then I really don't like my oil pressure being at 10psi...
My truck's pressure stays at 30+ after driving it for more than an hour. 30 at idle, and from 45-50 driving at 2500rpm. that's the only reason I'm worried about the pressure really, cuz I have something else to compare it to.

 

what kind and grade of oil are you using and whats the temperature out there ?

 

The air in the line does not matter. Since the pressure is constant if it 40 psi at one end of the line its 40 psi at the other end of the line even if there is air in the line. That does not mean your gage is accurate just that the air thing is BS. You want to verify your pressure with a hand held gage. If they match then you gage is good.
You need 10 PSI per every 1000 RPMs. Any less then that and you will damage you engine. It might be time to move to a heavier weight of oil. What do you use now? 20w50 is a good oil for motors that have a little to much bearing clearance.

 

Couldn't have put it better...

 

It is normal for oil pressure to drop as the engine warms up. The oil gets thinner as it heats up. If you are getting around 10 PSI of pressure for each 1000 RPM the engine is in good shape. The reason for the car having a mechanical gage is probably that the stock gage was broken and the person that owned the car did not want to bother fixing it.

 

I agree with every thing said above. But i would recommend checking out your oil pressure and finding out if the gauge is good any way. As said above a hand held gauge can be a quick way to verify that your gauge is working correct.

 

OK, where can I get a hand held?
I'm using 10W30 oil in it, and the temperature has been between 55-65 during the day here...

 

well at least I know I am not the only one that has a brother thats wrong alot more then right. and more importantly that you to know.