Oil pressure issue

[florida2002m3]

So ive been searching FAQ this morning for about an hour (on company time) and have not come up with someone who has the same issue i have.

'74 2002 100K miles on it.

Driven a few miles every few weeks for about 2 years.

Changed oil last weekend. It had 10w-30, I live in Florida so i decided to change to 20w-50.

Drained the oil, pulled the filter, thought i had a filter in the garage; i didnt. Called stealership, no luck. Autozone had a STP S3816 that said it would work.

Fit like a charm. Decided to put 1 QT of lucas oil in and 3.25 of valvoline 20w-50.

Car starts right up. No oil light at all at idle.

Take it for a spin, oil light flickers around 3-5K sometimes more steady than not. Pull over check for oil blowing past filter, nothing, drove her home.

Idle, no light. (valve noise, and marbles, but thats another problem next adressed)

3-5K flickering light.

Is it possible that i only put in 3 qt of valvoline (by mistake)?

Will .25 low cause the light to flicker at driving rpms but not at idle?

This is the problem im thinkin.

Is the STP filter being stupid?

Ive never used any STP filter before.

Thicker oil causing the problem?

Temps are a chilly 65-70 f.

Lucas oil treatment the problem?

Those are a few variables i can think of.

Any other thoughts ideas?

As always, any and all help is greatly appreciated.

[SteveJ]

I don't think the switch to 20/50 is any issue.

What does the dipstick say (the one at the motor). Even with the oil level at the lower mark, normal driving should equal no light lit. If it is way low, then during driving the oil would be sucked up and spread arond the motor, possibly starving the oil pressure sender.

The filter could be suspect. It's not the normal one that you would see on these motors.

[florida2002m3]

I tried the simplest first. Added another .5 qt. i would check the dipstick but the po mounted it too shallow so it never reads too much of anything.

No oil light when revvin in the garage. We will see when i drive it to the gym in an hour.

Thanks for the help.

[Brian]

The oil pressure switches/sensors do fail. I had the flickering light, but was really close to home so just motored gently on. I had an extra switch and installed it. Problem (and the flickering light) went away.

Now I have an oil pressure gauge installed, which would have removed most of the doubt.

[c.d.iesel]

stupid oil filter .

what's your idle RPM ?(should be 850 rpm)

[florida2002m3]

Well i have yet to tune the carb or redo timing since its been sitting 99% of the time. So right now the idle is about 1000-1200.

[BLUNT]

Id get a gauge on it but Id check the wire to the sender unit for a short rubbing on something. Could just be a coincidence.

I have an m30 that takes 30 seconds for the oil light to go off sometimes longer. I can start the car and scrape all the windows on the car before the light goes out lol

[JohnS]

Decided to put 1 QT of lucas oil in and 3.25 of valvoline 20w-50.

What does lucas oil do? Is that the problem?

I'm a big fan of pure Castrol 20W-50 and a Mahle or Mann filter.

[Guest Anonymous]

different oil sumps hold different amounts. make sure your capaciity info matches the oil sump installed on the car your are measuring. For most certainty, fix the dipstick tube and purchase the correct dipstick. They are still being sold. Eliminate the guesswork, then measure the pressure at the oil sender (on the dizzy pod). It could be that your oil pump needs rebuilding. If you feel like playing around with it, once the level is correct, put LUCAS oil stabilizer or heavier oil in it. If that doesnt make the guage lite work correctly, pull the sender and clean the sensor hole. It might be plugged.