My wife’s Cayenne got the “Oil Pressure Low Warning!” I read many posts and many tried to change the oil pressure sensor which I did. Unfortunately, I swapped out the sensors. A couple of days later, “Oil Pressure Low Warning!”.

I purchase an oil pressure gauge and unscrewed the oil pressure sensor and replaced with the gauge to monitor the pressure. These were my results:

1. At idle (cold) started at 4.5 bars

2. At idle (90C) was 1.5 bars which per the manual is at spec.

3. Revved the engine to 2500-3000, it was at 3.5 to 4.5 bars

4. At idle (93C) was 1.0 bar??

5. Revved the engine to 4000, it was at 5.5 bars

6. At idle (94C) was 1.0 bar??

The manual and forums I read stated it should be 1.5 bars at full operating temperature.

I love the car and always do all the required maintenance. I change the oil every 3,000 miles with full synthetic.

My question: is 1.0 bar causing the “Oil Pressure Low Warning!”. I did not hear knocking during the revs. The engine felt strong. Could it be just a weak oil pump or something else?

Any thoughts or advice would be helpful!

 

What oil are you using? Might need one with a higher hot viscosity. Should be running at least a 5w40 so if running a 0w30, that's the issue. For the summer, you could likely even move up to a 5w50. If running Mobil 1, change to something else, like Driven DT40 for 5w40 or Driven FR50 for 5w50 or something from Liqui-Moly or Motul in those weights.

Did the low pressure warning occur close to the end of your oil service interval I've found from my Used Oil Analysis reports that Mobil 1 shears to a lower viscosity in a s few as 3,000 miles and why i stopped using it a decade ago.

 

For the past 3 and half years, I have been using full synthetic 5W30. Was using Mobil 1 exclusively and then started switching Castrol etc.

Actually, the light came on around the 1300-mile mark of the oil change. I checked the level it was fine.

The Porsche tech service bulletins recommend 5W30 from I think 0W40. I am going to try 0W40 and report back my results.

Not sure if this indicates that the engine may be wearing or the oil pump is weak because I have never had the issue before.

The Cayenne currently has 112K miles. Runs perfect.

 

Yup, you should really be using an oil with a 40 hot viscosity - that might resolve the issue right there.

 

Ditch the Mobil1. They shear to almost water-like visco, overnight. Factory-fill, German Mobil1 is NOT the same as USA-market formula, which is a Group III hydrocracked base, with the bare amount of additive pack. I suggest Motul 8100 X-Cess 5w-40. Motul has excellent additive pack and the base is Ester.

 

If it doesn't get too cold where you live a 5w or 10w40 might be better, 0w40 sometimes specs out close to a 30 weight oil at 100C. A narrower viscosity range IMO is better as the oil needs fewer VI improvers to meet the specs.
Also "high mileage" oils usually runs to the thicker side of the spec. For example Mobil FS 0w40 is closer to 10w30 than 10w40.
Kinematic Viscosity @ 100 C, mm2/s, ASTM D445:
Mobil 1 0w40 FS: 12.9
Mobil 10w30: 12
Mobil high mileage 10w40: 15.3

If it stays above -15C or so I'd suggest running 10w40 at least to see if your oil pressure nag seems mollified. That said 1 Bar is plenty at idle IMO. It'd be annoying if the low limit is set above that.

 

Thanks for the tips on oil brands (Motul) and the narrower viscosity range.

The engine has been running fine no knocking, but one has to assume if I am getting an "oil pressure warning" the only clue may be 1.0 bar at 94C. I know there us a curve and not sure the extra 4C to 94C makes 1.0 bar the cause of the light.

My test is to change the oil to 0W40 (bought it already before the narrow viscosity post) and do the same test. Hopefully, the bar should be higher at 94C given it is thicker. Then reinstall the oil pressure sensor and drive it around to see if that was the cause of the warning trigger.

 

Perhaps consider 1-2 liters of 20w50 to bump that viscosity more significantly, then top up with the leftover 0w40 over time, see how it goes.

 

Here are my results with 0W40. I am hoping the light does not come back on.

At idle (35C) started at 4.3 bars

1. At idle (41C) started at 4.0 bars

2. At idle (46C) started at 3.5 bars

3. At idle (52C) started at 3.0 bars

4. At idle (59C) started at 2.5 bars

5. At idle (68C) started at 2.0 bars

6. At 2240 RPM (80C) > 5.0 bars

7. At 2400 RPM (86C) > 4.8 bars

8. At idle (90C) was 1.6 bars

9. At 4040 RPM (86C) > 5.5 bars

10. At idle (93C) was 1.2 bars

11. At idle (94C) was 1.2 bars

If there are any Porsche techs, do these numbers look normal?

So far no warning. The Cayenne runs great.

I am going to update if I see the sensor come back on or in a month.

 

You are correct about the 5W30. The VR6 engine requires oil that meets the Porsche C30 standard, otherwise the oil will cause pinging, which of course is very bad for the engine. Mobil 1 ESP and Liqui Moly are 2 brands that have the C30 certification standard. I'm sure there are others too.

 

Thanks for the suggestion. I switched to 0W40 so far fingers crossed no low oil pressure light. I plan on updating again at 3,000 miles.

 

UPDATE: After 3,000 miles the issue went away. I switched from 5W30 to 0W40. Hopefully, the data and results can help someone else!

Thank to all!