My family and I are on vacation in Florida, and yesterday while driving, I got a check engine light. I had the computer scanned at Auto Zone, and it shows low oil pressure. I started monitoring the oil pressure in the onboard menus, and it gets as low as 22 psi. It goes up to around 37-40 at driving speeds, but dips into the low 20s at idle.

Just before vacation, I changed the oil, and used my normal, Mobile 1, 5w30 synthetic, with a K&N filter. I have always had good luck with this. The car has about 130k miles, and we are from Tennessee, so while the temps here are a little higher, it shouldnt be that big a difference. Its been between 94-97 degrees all week. The car made the entire trip down, and several days of stop and go traffic, before this happened.

Am I looking at a viscosity issue, or am I going to be putting an oil pump in my car soon? I thought about having the oil changed to a 10w40, to see if this helps. Any suggestions?

 

I'd check it with a mechanical gauge first to determine if its the pump or the sender.

 

22 psi hot isn't low for a 5.7...my Charger gets as low as 18 psi if it's hot enough or been run hard enough at idle and that's with 5W20 synthetic. You may have had a sudden drop or your sensor may be going. Do you have your MDS turned off? 5.7 hemi calls for 5W20 for proper MDS operation. What was the actual code number?

 

MDS is still on, and I didnt ask for the code. He plugged it into the computer, and it had two readings, both said low oil pressure. As I am researching, 22 psi does seem to be ok. Im hoping it was just a little low on oil, and hasnt reset the codes yet. I typically put 5-1/2 qts in on an oil change, with a full filter. Then I run it for a few minutes, and check it cold the next day. Then I add what it needs. We were a little rushed before leaving, but I added 1/2 a qt yesterday to be safe, but the check engine light persisted. Its perfect today on the dipstick, but I havent started it yet.

Then again, it could be the sensor. Ill keep an eye on it. I cant change anything while Im away from home. We brought everything but the kitchen sink, and tools to work on a car.

 

O.K. I just started the car, and with it "cold" (not very cold when its 97 degrees outside) the pressure is 56 psi, and the light is still on. The engine isnt making any funny noises, and runs just fine. Im guessing its the sensor. Ill keep an eye on it, and look for a sensor when I get home. I also will look to make sure It didnt get unplugged, before I buy one.

 

Normally when your sensor goes **** up you get P0520 and it pegs out at 99psi

 

Also with the MDS still on, you're using the wrong weight oil. Proper MDS function requires 5W20 in 5.7's and 0W40 if I remember right in the 392 auto's. That's why I asked if it was still enabled.

 

I know it says 5w20 on the cap, but I went to 5w30 after 100k, as I have read it works better with high mileage. The car has 130k now, and I have never had this problem before. I took it to Florida last year, and Alabama, and Texas, where the temps were 105 plus, and never had this happen. For what its worth, almost as soon as we left Florida this morning, the light went out. The pressure stayed at 49-51 at cruising speeds, and never dropped below 21.

Would the 5w20 have prevented this? Or rather is the 5w30 causing it?

 

Could be either, but your oil pressure range cruising and the low 20's at idle when hot is normal.

 

Its pretty much a fact getting away from the recommended 5-20w will cause MDS issues. The old thicker oil is better is myth.

The cheap try is to toss a sending sensor in her and hope. But I would still worry and keep an eye on it. You did not state the year model,, sigh....