Old Manual Oil Pressure Gauge at Idle

[Chief Brody]

I took the blazer out on the interstate today and it was running great. I pull up on the off ramp and happen to look at the oil gauge and notice it is sitting at near zero at idle. It immediately jumps to 45 as I give it gas. I have never noticed this before. It has plenty of oil, I don;t hear anything or smell anything...the PCV valve is in place...there is no oil leak.

Is this normal for these old manual oil gauges?

 

[76k5blazerr]

Mine does the same thing.

 

[dremu]

Once warmed up, the oil pressure will be lower at idle and then raise with RPM, yeah.

Depends on how close to zero it is though; could be the gauge is inaccurate, could be the oil pump on its way out, could be phase of the moon.

I don't remember mine going below, I donno, 10-15 PSI.

-- A

 

[Chief Brody]

It didn't used to do that, I think I might have blown some debris out of the oil pressure line when I had it up to 85 on the interstate today,

 

[diesel4me]

The 350 I had in my 72 K5 used to do that if I used Amalie oil--I noticed the oil pressure on the aftermarket S-W gauge would be 10 psi less at highway speed than usual (like 30-35 psi instead of 40-45 psi..)--and when I came to a stoplight,it would fall to less than 10 psi,when before it never went below 25 psi..



I had used nothing but Castrol GT 20W-50 in it for years,then when I started working at a different parts store I tried Amalie oil in it,and it didn't like it..tried 20W-50 at first,then 10W-30 when it started getting colder..and the gauge started making me nervous,when I saw readings as stated above..
It was worse with the 10W-30..the gauge barely came off zero at idle after a long highway run ...

I switched back to Castrol and the oil pressure went back up to normal--for the hell of it I tried Valvoline 20W-50 and Wolfs Head 20W-50 when it needed an oil change and I didn't notice any change in the readings.
I suspected the Amalie lost a lot of viscosity after it got good and hot..
I always ran a WIX 51794 oil filter that held 2 qts too..