CharlieL

Last month I changed the oil in my 82. I used Mobil One--15W-50.
After about 500 miles my oil pressure light started flashind at low idle (800rpm or so). The weather here in New England is starting to get a little colder and I wonder if I chose the correct weight oil for this climate. The gage shows 5 bars or so when driving and 1/2 bar to 1 bar at idle.

WallyP

I don't think that either the oil viscosity or the type is a problem.

Break the possibilities down...

Low Oil pressure or faulty indicator: Since the gauge and light are separate indicators, and both show low pressure at idle, you probably actually have low pressure.

Either you are not developing oil pressure, or the pressure is leaking off. Not an easy way to tell (that I can think of). On an S4 or later, the plugs in the cam saddles are the first suspects, but you don't have those.

I'm sure that some of the 16-valve guys will have some suggestions...

IcemanG17

very odd.......does your 82 have an oil cooler? If it does its possible the oil cooler thermostat is stuck open.....that will cause low pressure at idle when warm...... Its an easy fix to change the springs....

If you don't have an oil cooler, which I don't think 82's do....then your best case scenario is a faulty sender...BUT since its a 2 output sender, 1 for warning light and 1 for pressure....since they BOTH are reading low.....then it appears to be working properly...

My other concerns are .5-1 bar at 800 rpm is TOO LOW.....my racer (84 no oil cooler) comes off track with oil temps near 275F at idles at 900rpm with pressures of 25-35psi (1.7-2.4 bar)

CharlieL

No oil cooler on my 82.

IcemanG17

Okay.........here is my advice.....run it for a short while....say 500 miles...hopefully in a couple long trips.....vary the rpm up and down.....but not above redline....drain it and take a sample....send it to Blackstone

http://www.blackstone-labs.com/

depending on what the results are will determine the next steps.....at this point I am cautious that the sender is accurate.....so the only answer for low pressure is loose (worn) bearings.....which the analysis would tell.....

Of course the faster answer is cut open the filter.....if you still have the old one would be GREAT..... if you engine is dying....the filter will tell all......don't ask me how I know

Barry Chan

the last time i got warning light was before i switch from 5w40 to 20w50.
with colder climate you should show higher pressure than 1/2 to 1 bar
mine idle at 3 after warmed-up and i am located in the northwest
check the oil level, maybe a new leak somewhere?

CharlieL

Barry,
Oil level is fine.
I'm using 15W-50. Is there a big differance between this and what you use--20W-50?
Charlie

Hilton

In an '82 with no oil cooler, the first thing I'd suspect is the oil pickup. They can crack or come loose and suck air.

Your idle oil pressure is very scary - if its really 0.5bar you'll have metal in your oil filter. Time to remove the filter, cut the end off and open out the pleats of to examine for metal particles.

I wouldn't be driving the car another 500 miles.

Hilton

Here's a similar thread from an '81 - just for ideas and other possible causes.

Ended up being the oil pickup, but there were 4 pages of discussion prior which might provide other insights.

https://rennlist.com/forums/928-foru...lp-please.html

Barry Chan

they are almost the same.
so no oil pressure means no oil flow...are you hearing any noise...valve tapping...

Maleficio

I once fixed a low oil pressure problem by replacing the ultra-cheap filter with an Amsoil filter. But the pressure was low across the board, not just at idle. Still, something to think about, and definitely the cheapest way to start troubleshooting.

Maleficio

Also, consider that you didn't have this problem until you switched to a heavier oil, hence a new filter, too. I've never seen a heavier oil lower oil pressure before. I'm calling the filter.

Sorry, you didn't mention changing to heavier oil. I read it too fast.