I bought an 86 SE V6 a few weeks ago, and on cold starts the oil pressure pegs the gauge max. Once the car warms up the oil pressure seems fairly normal reading just below half at idle and increasing oil pressure with throttle. I wasn't to concerned about the high oil pressure until today I found a pretty significant leak that looks like it's coming from my oil filter. I'm wondering if the high oil pressure could be the cause, or if there could be something else going on. Thanks for your help.

Is this the PO's oil or did you change it? A single weight oil would tend to read that way.

quote Originally posted by willyt: I bought an 86 SE V6 a few weeks ago, and on cold starts the oil pressure pegs the gauge max. Once the car warms up the oil pressure seems fairly normal reading just below half at idle and increasing oil pressure with throttle. I wasn't to concerned about the high oil pressure until today I found a pretty significant leak that looks like it's coming from my oil filter. I'm wondering if the high oil pressure could be the cause, or if there could be something else going on. Thanks for your help.

Yes, High pressure can make the filter to leak or even fail outright.
Example: The "cans" are only make to handle X psi safely. Exact X value depends on brand and often model w/ generally cheap ones have weaker "cans." Can = outside and flange w/ threads.
And this isn't only problem can cause by high pressure.

Likely PO put heavy oil to hide low oil pressure problem common to all w/ this V6 engine... Fiero, Cavalier including Z24, and others.
If true, sucks to be you because God knows what other problems just waiting to crop up.

You need a mechanical gauge to see if you have a dash gauge w/ problems. If both match numbers w/ engine cold and hot then have heavy oil, F'd filter, or other problems. Mech gauge might read > 80 psi = to "Peg" dash gauge.

If you change oil and filter now w/ 5W-30 (Factor spec, Can run 10w-30 or maybe 10w-40 outside of winter.) and get low pressure, the engine has problems.

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quote Originally posted by willyt: I found a pretty significant leak that looks like it's coming from my oil filter. I'm wondering if the high oil pressure could be the cause,

Is the filter tight?

As Ogre said, you can change to 5-30 oil and install new filter to see where you stand.
If pressure is very low at hot idle with 5-30, go to 10-30 or 10-40 oil for time being.

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[This message has been edited by fierosound (edited 05-02-2020).]

I changed the oil with 5W30 when I got the car, is the high oil pressure at cold start/high idle uncommon or an issue?

quote Originally posted by willyt: I changed the oil with 5W30 when I got the car, is the high oil pressure at cold start/high idle uncommon or an issue?

High pressure at cold start is common. My cars peg the gauge all the time on startup.
As long as pressure at hot idle is not so low as to be in Red - you are good to go.

Either filter has loosened off or can be faulty. Tighten or replace.

Also, sometimes o-ring from old oil filter sticks to block and goes unnoticed.
Then when you install new filter, you now have TWO o-rings - not good.

[This message has been edited by fierosound (edited 05-02-2020).]

quote Originally posted by fierosound: High pressure at cold start is common. My cars peg the gauge all the time on startup. As long as pressure at hot idle is not so low as to be in Red - you are good to go.

This is Not normal w/ 5w or 10w oils.
Not even Straight 30 unless weather is cold like below ~ 50°F. A bit higher w/ engine cold is ok but pegged at/above 80psi in not.

10w start to gel ~ 0°F/‐18°C
5w rated well below 0°F
That's w/ "Dino Oil." Syn Oils flows better at rate Xw because far less to no Wax.

Again, Get a mech gauge to test any time you have low or high oil pressure.
Dash gauges lie often and numbers on Fiero gauges and many others don't mean much.
My dash gauge and sender has been change several times and still lies all the time because wire issues somewhere in the car. Occasionally is accurate showing ~ 40psi. Even ~ 45Ω and ~ 90Ω resistors between OP plug and engine reads way higher 40 or 80 psi on the dash gauge.

Oil Pressure should be in Factor Spec regardless of RPM and Heat vs cold.
V6, VIN-9, 30-45 PSIG
L4, VIN-R, 36-41 PSIG
(Source, ALLdata)
See my Cave, Oil and Filter

Old style OP sender have problem and V6 w/ AC have that Very Long tube feeding that may have problem too.
See my Cave, Oil Sensor

Even if you install new filters and then they see OP push above 80 psi... The filter flange can warp and leak at the "O-ring." More so w/ cheaper filters.
Flange Warping and/or Body blowup could be so bad @ high pressure that the guts won't seal let dirty oil bypass the media.
Or Filter media can fail and block flow after. That can make bypass valve in the engine to bypass dirty oil around the filter.