Engine Hot idle oil pressure


Jun 7, 2018
Dublin, OH
Hello all, I have a 1991 lx 5.0 with a 347 swap with a Holley hp efi system. I do not have my factory dash, and all of my gauges are electronic/digital running through the Holley system.
At cold start I have oil pressure of a little over 50 psi, and as it starts to warm up, the pressure begins to fall, when I’m cruising on the streets it’s typically 50 psi even when it’s hot, but if I sit and idle, it drops below 30 psi, about 26-28 psi. I use 10w-40, and am wondering if this could be an issue, I checked my oil level this morning and it was good, but I am thinking that as the oil heats up, it gets thinner and that could be why the pressure drops. Could it be the weight of the oil causing this? Or is 25-30psi at hot idle (20 minute highway cruise) normal/enough pressure?
Any input helps, thanks
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Mod Dude
Apr 6, 2011
Hillsborough county
I would consider that normal, just keep an eye on it. if in doubt cut the filter open and check for metal, the old rule of thumb was 10psi per 1k rpm.

John Dirks Jr

there is enough sticking out to grab on to
5 Year Member
Jun 28, 2013
Nothing wrong with those oil pressure numbers

How fresh is that engine? If its in decent shape I recommend 10w30 full synthetic and dont look back. Even if the thinner oil drops the idle pressure lower, I wouldn't worry.


SN Certified Technician
Aug 8, 2003
10psi per 1000rpm is usually the rule of thumb.
I've had a bunch of engines, most usually held about 20psi at about 800rpm when in proper condition.
My one engine that burned oil, was at like 15, then 10, then 7, then it was retired.
And believe it or not, that took years to happen over time.
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John Dirks Jr

there is enough sticking out to grab on to
5 Year Member
Jun 28, 2013
I had a 232 inline 6 in an 1971 DJ5 postal jeep that I owned. Delivered mail with it on a rural route for 9 years. Hot idle oil pressure almost zero!

It leaked a little and burned a little. I always would add a qt when it needed it. Couldnt kill it. It ran fine as long as I owned it. I eventually sold it when the USPS gave me a new gov owned delivery truck. After owning that old jeep, I was never afraid of low oil pressure at idle.
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