Chrysler Repair: 2.5L V-6: oil pressure warning light on at idle, chrysler cirrus lxi, chrysler cirrus

Question
Hi Roland,
I have just bought a Chrysler Cirrus LXI 2000 , 2.5 V6 engine, 100K km and it seems that I have a problem. Everything works just fine, but, once the engine gets warm, my oil pressure light comes on, but only when I'm at a stop or idle and when I go the light goes off right away. I changed the oil and I even added some oil additive but it is the same. The guy that changed the oil told me that the sensor seems to be recently changed, so I was wondering if I should try and change it again...
Do you think that this could be a problem for the engine?
Thank you very much!

Answer
As an engine wears the resistance to oil flow in tight spaces reduces so it moves through them more easily and the overall pressure in the system drops.  One step would be to measure the actual oil pressure when the engine is idling and warmed up. I doubt it is below the minimum specification of 6 pounds per square inch, but it may be worth paying to have that done anyway. You know the warning light is working... but I suspect it is set to go 'on' when the pressure drops to less than a number greater than 6 psi. If you want to have it measured, then ask also if the pressure at 3,000 rpm is greater than 35 psi which is the other specification. At the time of the measurement the pressure sensor which is what turns on the light has to be removed, so if the pressure seems to be well above the specified minimum at idle you could ask them to replace the sensor due to the possibility that it is too pessimistic.
This is fairly common with all makes/models. Your idle rpm too could be a little on the low side which means the pressure is going to be low enough to turn on the light after the engine warms the oil, which also lowers the pressure a bit.
But in my experience I would not be concerned for the moment, and another approach which doesn't involve labor costs is to instead, the next time you change the oil, increase the 'weight' by one step*, which increases the viscosity and thus will raise the pressure at idle so that the light will usually not come on anymore. Another approach would be to buy a sensor for the light and replace it yourself, as the present one may be off-value. Either of those approaches don't have any labor charges if you do it yourself. The sensor is located near the oil filter and has a single gray-colored wire. It is on the side of the engine closer to the cabin, and you would want to jack up the right front tire and support the body and jack stand while doing the replacement/oil change.
The only time you really have to be concerned is if the light comes 'on' when you are moving and the rpm is higher than about 1,000 rpm, as that could mean there is insufficient oil reaching all the moving parts.
The oil costs the same no matter what 'weight' you buy, so increase it one step and see if that eliminates the warning light problem. Also, if you have been buying synthetic oil you could switch to conventional oil which produces a higher pressure reading for the same operating conditions. It costs less as well.
Should these approaches still lead to the oil pressure being below 6 psi at idle, then it would probably require that the oil pan be removed and the inlet screen of the oil pick-up cleaned and the oil pump itself evaluated for rebuild to increase its pressure output. But that would come later and be more costly to accomplish.
Roland
*If you have been using 5W-20 try instead 10W-30, for example; or if 10W-30 try 20W-40.