92 GMC Yukon OIl Pressure

[Aaron Westervelt]

So my 92 GMC Yukon, has 255,000 miles on it. Ive noticed in the past few months my oil pressure has dropped to about 8psi at idle. At WOT itll go up to 35-40psi then once im cruising down the highway itll settle around 18-20psi. I know this is low.
My father an old farmer claims old small blocks at idle only require around 7psi and 15-20 while driving. He tells me to ignore it. However it bugs me just seeing the gauge and I'm aware factory gauges are junk.....
Would it be any harder on the motor to switch to 15w-40? I'm trying to baby the old girl for at least a while before I pull the engine, seeing as how I just dropped 1700$ on my transmission a few months ago.

Also I've lurked on here for a while but this is my first post, I hope its in the correct place. thanks

 

[Aaron Westervelt]

Also should be noted, I still have very good compression, and it doesnt leak or burn a drop of oil since I've had it.

 

[Dan_Frisbie]

Although we're used to seeing 30-60 psi, I have always been told that a SBC needs 10 psi for every 1000 rpm. I've never had one that low, so I can't guarantee that statement.

 

[Aaron Westervelt]

Thank you, I have never had one drop that low either. thats what Ive always been told also.

 

[DerekTheGreat]

Like you mentioned, could just be your sending unit is toast. I run 5W-40 in the "new" engine in my truck that has 140k on it. There's a dude on here running 15w-40 with no issues but I'm leary of that for cold weather start-ups, stuff is like syrup when cold and especially if it isn't synthetic. For reference, my truck when cold indicates 60psi @1,200RPM, about 50psi at 750RPM. Hot it is about 45psi @1,200 and 20psi @750RPM.

 

[GMT_TANK]

My guess is the oil press. Sending unit. But those gauges are crap, you can test those gauges by sending using a analog gauge tester


Sent from my iPhone using Tapatalk

 

[c1500deathtrap]

Thats plenty of pressure. If yyou want try 10w40 1st. its what i use.
>effect of viscosity changeshttp://www.hotrod.com/articles/ccrp-0911-small-block-chevy-oil-pumps/
>

Although we're used to seeing 30-60 psi, I have always been told that a SBC needs 1 psi for every 1000 rpm. I've never had one that low, so I can't guarantee that statement.

It's 10 psi per 1000 rpm. Please don't try to run 1 psi per 1000rpm

 

[Dan_Frisbie]

Thats plenty of pressure. If yyou want try 10w40 1st. its what i use.
>effect of viscosity changeshttp://www.hotrod.com/articles/ccrp-0911-small-block-chevy-oil-pumps/
>
It's 10 psi per 1000 rpm. Please don't try to run 1 psi per 1000rpm

MY MISTAKE! I will edit the post. Thanks for pointing that out.

 

[Aaron Westervelt]

I knew what you meant. I also didnt catch the 1psi per 1000. Thanks for all the replies, my gauge was off by about 10psi. Still low but its worn out. Ill probably change the sending unit and if it doesnt change I'll just run it til blows and start rebuilding one of the what seems like thousands of small blocks we have laying around.