DanielRicany

Hello everyone. My 1985 Corvette is experiencing low oil pressure at idle only.

I drove it today and the oil pressure at idle was as low as 11, but mostly around 12-15 when the oil temperature is 218*F. My idle RPM is set to 900 RPMs by the way.

Cruising at 2300ish RPMs the oil pressure was about 50.

Any idea why this might be happening?

Thank you.

antfarmer2

10 lb at 1000 rpm is good

Benny42

What oil are you running currently? Its a bit low if your engine isn't pretty well worn, but not
too bad. Syn or conventional, weight?

DanielRicany

It was Mobil 1 Full Synthetic 10w30

antfarmer2

The gauge can be off too.

JrRifleCoach

A new problem? Or just an observation?
Old school rule of thumb 10psi for every 1000rpm.
IMHO, your good. Just keep a watch for other symptoms, like holes in the oil pan.

kenmohr

Just turn your idle up. LOL sorry couldn't help myself. I second the check gauge or sending unit.

WVZR-1

OP - you asked about the "gauge check/sender" earlier this month and mentioned buying resistors to correct which I thought odd BUT is this a new or related to OR?

How are the 2 threads related? What/how did you attempt correction with resistors?

https://www.corvetteforum.com/forums...-question.html

DanielRicany

I only used the resistors to diagnose the cluster. The new sensor appears to be accurate when compared with the mechanical gauge.

Strange because the oil pressure is great when driving...

WVZR-1

I assumed that's what the resistors were used for but thought I'd ask.

You've confirmed the dash unit and based on the very wide +/- tolerances of the sender manufacturers I'd think your good to go. If you've question check or recheck the sender for the resistance it's producing.

exitwound

I use Mobil 10w60 fully synth. Extended life/track oil in my 150K mile '87. Changed every 15k miles or 2years (..the old oil is still fine and my mate uses it for his MGB hillclimb car!)

bjankuski

You may have some worn bearings but overall it does not seem like it is worn out yet. The reason the idle oil pressure is lower is that the pump is turning slower and pumping less volume. Since the bearing clearances do not change with RPM the pressure will be lower at idle (The leak stays the same with less oil volume available)

WW7

I ran my original motor for years with just 12 pounds oil pressure without a problem...The important thing is if the pressure rises when the rpms rise...If your pressure rises to 50 psi at 2300 rpms I would say you should be fine..If your oil temps are at 218 degrees, that may be one of the reasons your pressure is low. My oil temps usually only gets to 208-210 unless the air temps are real high and Im moving slow for an extended period of time......WW

JackDidley

I'd drop the oil pan and look at the bearings. You can replace the rod and main bearings in an afternoon. If you do it before the crankshaft is hurt, its no big deal.

gerardvg

Hi

First things first, check the oil pressure and confirm if the dash readout is accurate. The TPI should have 20w50 oil, the synthetic oil you have is a lot thinner hence lower idle oil pressure. However 10psi at idle is fine, if you want more pressure fit a high volume oil pump.
I did that to my 383 engine that was built with more clearance for the hard life and rpm she will be exposed to, I wanted more oil flow / pressure and the high volume oil pump did the job.

Just remember a high volume oil pump needs a heavy duty oil pump drive shaft and extra oil capacity sump, my sump was enlarged at the sides. As a precaution so it doesn't pump all the oil out of the sump before it can return at high rpm

A Peter C4

My 1994 LT1 with 103000 miles hood decal says 5w30 mobil 1 ,I have changed to 10w40 extended life Mobil1, it helped raise idle pressure about 10 lbs. at idle hot,I like this ,much better peice of mind when hot and idleing.