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2005 Chrysler 300C Intermittent Low Oil Pressure & subsequent P0524 OBDC

Correct. 5W20 is also recommended for the 5.7 Hemi.
I’m going to look at potentially going with a single higher viscosity oil and also see what options are available to adjust the idle speed.

Since your mechanic has verified your oil pressure is okay with a mechanical gauge, you are avoiding the easier first steps. As recommended already, change the oil pressure sending unit. Perhaps it was never actually replaced in the first place or is damaged. Also check the connector and wiring.

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I do remember my 94 Saturn Sedan listed at least 2 different options…I wonder when manufacturers went away from that? Probably when CAFE standards got really strict for gas mileage?

In the case of the 5.7L Hemi in this car, the motor oil is used to operate the MDS so viscosity is critical to keep this system operating properly.

This is one reason why we generally recommend it get checked out by a mechanic. A low oil pressure car can live on for quite a while, If you have the option to return the car I would.

I think you are right. It is all about the CAFE standards.

For example, I have a Mitsubishi Mirage. Many like to rag on this car for being a “third world” car. Anyway, they specify 0W20 in the US. Apparently the same exact engine overseas calls for 10W40 in countries where high quality synthetics are not widely available.

Owners of the car here have done oil analyses on their engines to see if this holds true. Apparently they see no worse wear using thicker oils and some even see better. These use solid lifters as well so that isn’t impacted by oil viscosity.

They will spec the thinnest oil possible for US sold cars. Some will not do well with anything thicker. If I were to experiment with a thicker grade, I would probably go to a 5W30 next. Again, checkout forums for people familiar with this engine. I am not at all a Chrysler guy.

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I know this is an old thread, but, may help the OP and others.
Low oil pressure light is a well known issue with the 2.7L Sebrings,
and may be the problem here. My old '02 Sebring convertible used to have the oil light flicker at idle on a hot day - scared the pants off me. Problem is the heat & the oil pressure sender itself.
Chrysler made an “upgraded” sender for the 2.7, which consisted of sender with an extra wire to bleed off heat.
If your issue is the same, you may be able to cure problem with new OEM sender, (Check to see if Chrysler shows more than one part number, or upgraded # for your car/engine, talk to guy at Dealer parts department) or, you may be able to cure by just cleaning things up, since they tend to let some oil leak past.

The area where the sender is located needs to be clean clean clean, for good ground (?), and, ditto for the connecting wire(s)!!
Remove sensor, spray area liberally with carb cleaner, spray and clean the sensor, and let dry, spray the wire connector, and the inside of the electrical connector.
If using the original sensor, and there is a second (unused) terminal, add 5-6 inches of copper wire to make the “upgrade”
— Hope this helps —