Low oil pressure at idle?

[Jetronic]

yes. internal leakage in the pump stays the same regardless of rpm and bearing oil consumption likely drops at higher rpm. in any case, double pressure doesn't mean double oil flow through bearings or spray nozzles.

Drop rpm below 400 or so and the oil pressure light might flicker...

 

[Avery4]

yes. internal leakage in the pump stays the same regardless of rpm and bearing oil consumption likely drops at higher rpm. in any case, double pressure doesn't mean double oil flow through bearings or spray nozzles.

Drop rpm below 400 or so and the oil pressure light might flicker...

Good to know, thank you! I was thinking the engine's internal restriction stayed relatively constant throughout the RPM range and any change in pressure was mainly due to the pump pushing more oil at higher RPMs, but that may not be the case.

In any case I don't think having only 13-14 PSI oil pressure at idle is a problem since it doesn't need much pressure at idle and the pressure is good at any RPM above idle, so it's not like the engine is going to be running under load without adequate oil pressure.

 

[Avery4]

Oil pressure is still pretty much the same, 12-14 PSI at warm idle (oil at 185 ish degrees). It still just seems wrong to have so little pressure at idle. The other day I got stuck in traffic and my oil temp got up to 195 degrees and the pressure was right at 10 PSI when I was idling. But if I didn't have an oil cooler, I'm sure the oil temp would have been significantly higher and the pressure would have dropped more. And if I was using the 5W20 oil that is recommended in the manual, the pressure would have been even lower.

With the recommended 5W20 oil at 210 degrees, the oil pressure drops to 6 PSI at idle. I just can't imagine that pressures that low with the recommended oil at an expected operating temp would be normal.

 

[atikovi]

5W50 is worth a try.

 

[Avery4]

5W50 is worth a try.

Not sure about 50W, but I am considering using the thickest Honda approved oil (5W40) next oil change instead of 5W30. I may also drop the oil pan to inspect or maybe just replace the oil pump and check bearing clearances and condition.

But on the other hand, since oil pressure is good at all other RPMs and there are no other indications of trouble such as nasty sounds, glitter in the oil, etc, I'm not sure that the engine is bothered by the low oil pressure as much as I am. I would think if something was wrong, the oil pressure would have dropped somewhat since I installed the gauge almost 2 years ago and it hasn't. Maybe that's just how these engines are.

 

[mightymousetech]

Sounds like you are trying to fix normal operation. This is why cars don’t have oil pressure gauges anymore.

 

[wag123]

I reiterate, IMO you are OK.

 

[Avery4]

Sounds like you are trying to fix normal operation. This is why cars don’t have oil pressure gauges anymore.

So would you call 6 PSI of oil pressure at idle with the recommended weight of oil at 210 degrees normal operation? Seems low to me, but I don't have another similar engine to compare it to.

 

[vavavroom]

12 psi seems a bit low but if they say 10 psi is still normal don't worry. How do you know your oil pressure sensor and gauge are dead-nuts accurate and precise? Somehow I managed to post this reply in the wrong thread earlier today.

 

[Avery4]

12 psi seems a bit low but if they say 10 psi is still normal don't worry. How do you know your oil pressure sensor and gauge are dead-nuts accurate and precise? Somehow I managed to post this reply in the wrong thread earlier today.

10 PSI at idle is the minimum spec for 5W20 oil at 80 degrees C (176 F) and 50 PSI minimum at 3K RPM. I have no way to know exactly how accurate my gauge is, I have thought about renting a mechanical oil pressure gauge from the parts store and comparing the readings.

Pressure at driving RPMs is good. At 2K I get 45-50, at 3K 65-70, and it maxes out around 80 at full throttle.

 

[02SE]

IIRC, the oil pressure light comes on at 5 PSI. I'd say you're fine, and overthinking this.

 

[Avery4]

Sounds like you are trying to fix normal operation. This is why cars don’t have oil pressure gauges anymore.

If these cars came with oil pressure gauges this would be much less of a problem since information on what normal oil pressure is would be much more readily available.

 

[Avery4]

Update: When I changed the oil last night, I decided to pull the oil pan to check the oil pump and bearings. The 2 rod bearing caps I pulled off basically looked like new as you can see. I couldn't find my Plastigage to check the clearances but I'm sure it's fine.

However, I did find that the oil pump's pressure relief valve piston had a slight rough lip on it that prevented it from sliding freely and possibly seating completely. A few minutes with a file and 400 grit sandpaper fixed that.

I also changed the oil pump pickup tube gasket while I was in there for piece of mind since it was so cheap and easy.

The results? At the same oil temp (185 degrees) oil pressure at idle is now slightly up to around 15 from 13-14, at 2K RPM it is slightly up to around 53 from 48, and at 3K RPM it is up significantly to around 78 from 70 max. Pressure still maxes out at around 80-85 at full throttle. Now it basically holds steady at around 80 from 3K RPM up with a slight drop as VTEC kicks in.

Same oil that I have been using (Pennzoil Ultra Platinum 5W30), only difference is this time I used a K&N Performance Gold filter instead of my usual Wix since the parts store was out of Wix, but that seems like way too big of a difference to be caused by a different brand of oil filter alone.

As good as the bearings looked I'm not worried about this anymore. Thank you very much to everyone who responded, your input is very much appreciated!

 

[DGXR]

Your idle oil pressure is within spec so it's fine. 45 PSI at 2000 RPM is a significant jump so I would not worry one bit. If fact, I suggest going back to 0w20 at the next service. Also, you might want to mount the oil temperature sensor where a true oil temperature can be read, maybe in the oil pan or at least closer to the oil cooler feeder line (not return line)? Just my $0.02

 

[Avery4]

Your idle oil pressure is within spec so it's fine. 45 PSI at 2000 RPM is a significant jump so I would not worry one bit. If fact, I suggest going back to 0w20 at the next service. Also, you might want to mount the oil temperature sensor where a true oil temperature can be read, maybe in the oil pan or at least closer to the oil cooler feeder line (not return line)? Just my $0.02

Thank you very much for your input! After seeing how good the bearings look I'm not worried about it. I may switch to 5W20 oil next time to bring the pressure down a bit now that I am seeing 100+ PSI on cold starts and ~80 PSI at just 3K RPM fully warmed up, I think bringing the pressure down a little wouldn't be such a bad thing. Minimum spec at 3K RPM is only 50 PSI.

I have the oil temp sensor screwed into the return side of the oil cooler sandwich plate. My thought was that the temp of the oil that's on it's way to the engine was most important. However, my oil temp gauge is a dual gauge since I used to use the other readout to monitor ATF temp, but now that I have a manual trans its temp doesn't matter much so I may move it's temp sensor to the supply side of the oil cooler so I can see temps in and out of the cooler at the same time.