i got a 77 olds 88 had a oil pressure gauge put in when the engine was rebuilt it used chevron supreme 20W50 and kept using it till the engine got broke in which the engine is at a bit over 1000 miles which is the break in period now after the engine breaking period i did change the oil when the old oil expired i changed oil weights i put in castrol GTX 10W30 and before the 20W50 my gauge read 30 to 35 PSI at a stop now it reads around 25 to 20 PSI at a stop and the tubing you get with the oil pressure gauges its a clear tubing and the oil has a soapy look to it it or looks bubbly and i have no idea on what went on. i can't remember if the 20W50 did the same thing its impossible that the new oil has a bubble look to it as teh only thing that was off was the oil pan plug to drain the oil nothing else was off so water or air did not or could not of gotten in but turns to normal after the car cools off my gauge never idled at 20 or 25 whent eh 20W50 was in it idles normal oil pressure when you go and in park it is at the normal pressure which is 40 to 30 in P but at a stop now it goes down to 25 or 20 and no further down it does not go below 20 i have no idea on how to read a gauge is it normal for the oil pressure to be between 20 and 40? and i know below 20 is bad but 20 and above is it a bad thing? it bothers me to see the pressure at 20 im thinking on seeing what happens when i put in the 20W50 to see if it goes to what it did. will that work or should i try it. what should i do or what is happening and is it normal. i replaced the thing that goes in the front of the block and the tube goes in to the top but it did nothing the old one was leaking but the new piece did nothing its just the pressure at 20 PSI which bothers me or is it the normal number to be atOil pressure gauge tubing and pressure?first wasnt anything wrong with 20w50Oil pressure gauge tubing and pressure?I understand your worry being a new motor and you want every thing right you are running a lower viscosity of oil and you will have a lower pressure and yes the 20/50 had air bubbles in it as the 10/30. If it will put your mind at ease go back to 20/50 and see the exact same thing bubbles and a little higher pressure. It is fine enjoy the new motor and change the oil every 3500 miles.Oil pressure gauge tubing and pressure?Thinner oils flows easier, but dont show s much pressure on a gauge. That is common and norm.
20W50 will always read higher than say 10W30.
Now really 20W50 shouldnt have been used on a new rebuilt engine. Thats way too thick for a new, tight engine. 10W40 should be the thickest you run
Airin the oil is norm. It's called windage and crankcase pressure. As the crank, rods, etc moves in the crankcase the oil gets whipped around and causes air bubbles, foam at times, and plus the new rings takes time to seat and seal so you probbly have compression slipping past rings and entering the crankcase.. Norm takes 1500-2000 miles to fully seat rings
Oil pressure, you need a min. of 10 psi per 1,000 RPM engine speed with engine at running temp.. Higher is much better than lower..
But you are fine with as low as say about 8-12 psi at a hot idle (15, 20, 30 psi is even better though)
