High Oil pressure

[Tonhão]

My friends alfisti, the oil pressure of my 164 LS is a little higher than normal.

What does it mean? The engine can be damaged in any way?

And if I switch to a thinner oil, the pressure will increase or decrease?

[Richard2]

Some more detail would help. Are you talking about oil pressure when it is hot? What grade of oil are you running now. It's winter in Brazil, right?
What was your oil pressure before, what is it now?

[Roadtrip]

If you are depending on the car's gauge, don't. It's probably inaccurate. Connect a mechanical gauge to check on the accurate oil pressure.

[Tonhão]

There’s no chance that the oil pressure sensor work well? Mine is brand new.

I’m using 20W50:

Cold idle – 61 psi
Hot idle – 29 psi
3000 rpm – 50 psi
4000 rpm – 50 psi

Here, where I did these measurements, the winter is very mild, the minimum does not fall below 54 ° F.

Before the last service done in the cylinder head, the pressure was slightly higher than now, hovering around 58 psi.

[Michael Smith]

No need to use 20W50. Switch to 5W50 or even 0W40.

Although in Brazil the W number hardly matters, full synthetic SAE numbers are a tad misleading. Synthetic runs thinner than the number would indicate but protects better. Don't use conventional oil, use synthetic and run 5W50 or thinner, it will work fine.

[Richard2]

My experience with 0W40 was not good. The oil pressure dropped off and the engine was noisy. I changed it out right away.

[Michael Smith]

Factory fill for our cars was synthetic 10W40. Since the higher number is the only one that counts when the engine is warm I suspect your issue was brand related. Synthetics are hard to measure in comparison to the standard oil the SAE number refers to. I have found that different brands of oil with the same SAE numbers perform noticably differently. This has been true in several brands of engine.

I find that oil consumption increases when I use Mobil 1 0W40 as opposed to 10W40. Throwing in some Mobil 1 15W50 cures that.

Castrol Syntec 5W40 performs like the Selenia 10W40 filled by the factory. I have also used AGIP Sint 2000 5W50, Pennzoil 5W50 and Castrol Syntec 5W50 with good results.

I suspect conventional oil of 20W50 weight is a bit heavy for these engines even though nominally the same as synthetic 5W50 when hot. although European owners report using as high as 60 fully synthetic without issues. Generally speaking one should use the lowest summer weight number recommended by the engine manufacturer for best performance, which would be a 40 weight synthetic for this engine.

[Tonhão]

If I switch to a thinner oil, the pressure will be lower than now?

I thought it would be higher.

[Richard2]

It's hard to tell. Maybe yes, maybe no. An integral part of the oil pump is a relief valve that opens if the oil pressure gets too high. If you put in a lower weight oil, the relief valve will likely just run closed a little further. The only way to tell is to try it. I prefer higher oil pressure, but gas mileage is better with lower grades of oil. I ran Mobil 1 20W50 in my 1st 164S for 167,000 miles and really liked it. When I rebuilt that engine to put in my 2nd 164S it still had some of the original machining marks on the cylinder walls.