Oil light coming on at idle.

How is the oil level?

 

If your needle is not "dancing" is not your oil pressure unit, if you are using 5w-40 it happens from time to time, if the light turns off and the needle moves after you press the throttle a bit then you are fine, is one of those things that just happen from time to time in our cars (mine does it specially in hot days and as you said when you are in traffic), I was told by my mechanic that switching to 10w-60 would fix that intermittent gremlin.



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Hooking up a mechanical gauge to test the accuracy of the electric one is SOP for that diagnosis and not difficult.

Putting in thicker oil is a band aid and not addressing the problem. Unless the oil is ultra hot that is just not normal and should be looked into.

 

10-60 is for severe use. If it is needed to keep the light out in street use something is wrong.

 

Stepping ahead from the OP, I think this will be his next question.

What typically is wrong to have this symptom? Maybe just the top three possibilities would suffice.

Thank you much!

 

It can be a gauge problem. I have seen a couple with bearing problems. It can be a pump or a relief valve problem. It could also be a bad oil filter.

 

Brian ..While on the subject what is the normal/common oil pressure for a 360 430 and scuderia at 200 degree oil temp at idle

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Problem is (if I understood correctly) this has happened only once and if it is like my car it will happen again in some weeks or months so you can measure right now just to know if it is reading correctly, but your best bet was to get the reading when the light is actually on.
I was in the same position than you the first time that happened, performing forum searches and reading old threads, I found several people had the same issue and several mechanics (including mine) said it was "normal" in 360s.(normal meaning it happens from time to time)
While I agree that changing the viscosity is like a "band aid" and will not fix the underlying problem, it only happens sporadically and under certain conditions (i.e. hot weather, after a spirited drive, in traffic) I would be concerned if it happens in other kind of conditions and more often, otherwise you could be pursuing a gremlin.


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Correct me if I'm wrong but doesn't the sending unit serve two separate functions with separate controls, one for the gage and one for the low pressure warning light. One part of the sending unit is variable resistance (oil pressure). The other is just a pressure switch that grounds the warning light circuit when pressure drops below the set limit. If the gage is showing low pressure AND the low pressure warning light is coming on that's two indications of low pressure. Plus, my experience with sending units is that they tend to indicate high oil pressure when they fail. The OP's situation where the gage indicated low pressure and the low pressure light is coming on suggests that both are function correctly.

 

Being in the Instrument and Controls business, sending units do go bad occasionally. We always verify with a simple calibrated mechanical gage. You can speculate and try to mask the symptom with heavier oil but until you verify the sending unit is reading correctly you will never really know what the real problem is.

 

Wrong move as you are masking a problem !

 

I'd just put black tape over the gauge. Problem solved. *lol*

 

Your sender is fine and your gauge is fine.
Just did a major on my '99. The gauge was erratic, requiring a new sending unit.
The oil change utilized shell 5W-40 ultra helix.
The gauge frequently shows 15 psi hot oil pressure now. It did not do this before with the same oil but a faulty sender. I haven't seen the light go on yet.....however it hasn't been hot here since the major was completed.
IMHO the thicker oil isn't a solution. There are other conditions you'll create by using a higher viscosity oil. Your call if you wish to try it.
If it was me - I would not worry about it and just drive the car.
Question for you: what was your oil temp when you noticed this happen? Just curious.

 

Looking at the oil pump diagram, there appears to be at least 2 oil pressure control devices- might be an idea to look to see if these are seating correctly, will the oil hot and tick over revs you might be losing a bit of pressure- old spring in relief valve etc.?