The factory service manual states psi should be around 57 at 6000rpm after warmed up. Mine runs more than double that like most of your cars.

My question is, how do you know when your oil is at operation temp when we only have a coolant gauge?

That thing shows the engine is warm within 3 mins. of starting. Can someone with an aftermarket gauge give the rest of us a time estimate?

 

My oil psi after my car is driven for a while is around 35psi

 

Don't assume that the oil pressure gauge is very accurate without comparing it to a real external gauge where 1 psi increments can be read.

The only critical parameter is to not go below 14 psi IDLE [factory FSM spec] with the oil hottest [80 mph for 2-3 hours in 110F ambient].

Internal coolant temp gauges are purposely made inaccurate and heavily damped [slow to read changes once warm - overheat] to smooth the spikes.

An OBD2 scanner reads the real [what ecu works with] coolant temp within 1F...........watch the real temp vary 20F and the inside not move at all.

At higher mileage: One selects a summer oil viscosity and brand [Xw20, Xw30, Xw40, Xw50] that will not go below 14 psi [15-20][accurately measured] at hottest idle with the bearing wear you have!

Important to accurately check oil pressure every few years [30k] so you can graph the changes [bearing wear] to see when the engine needs retiring [200k, 250k, 300k].

I still exceed 14 psi [just 15-16 psi] with new HOT 10w30 Mobil 1 at 270,000 miles on my 15 year old Q45. Same as it measured with 200k in Summer 2000.
Frequent oil changes with synthetic can prolong a good engine almost forever.......unless you overstress it [rod bolts]......we service one 94Q with 343,000 miles.............it only has about 12 psi of idle oil pressure but used conventional oil so you would expect a little more bearing wear.....even though it gets 8 oil changes per year.

The new 3.5 V6 is a total redesign so we will need to wait a few more years [a decade] to see if it is compariable.

 

You might find this discussion of Yamaha [SHO V6-V8] oil requirements interesting........discussed oil requirements in DOHC engines and bearing clearances.
http://www.shoclub.com/lubrication-o...n-oilpart1.htm

G35 V6 = 0.0014-0.0018" main bearing oil film clearance --- wear limit 0.0026"
1990-96 Q45= 0.0005-0.0012" --------wear limit 0.002"

As you can see from above the bearing clearances of the 3.5 are almost double the Q V8 but that was necessary to trade off lower friction [HP increase] for extreme longevity [still the wear limit of 3.5 is only 30% larger.

The 3.5 clearances would explain the need for higher oil pressure.

 

actually the factory gauge is very accurate. I have run it side by side with an external gauge a few times and both units 9the other being a Defi) was dead on.

As for pressure, the factory manual assumes the oil is fully warm - that happens at a MUCH slower rate than the water temp reaches full operating temp. The oil temp gauge in my other car does not reach full operating temp until I drive the car for about 30 minutes

 

Guys I have a problem with mine in that after driving on a freeway for 15 minutes or so the oil pressure will slowly creep up to max 115 psi without any speed increase in 6th gear. Idle pressure will also be too high when this happens. If I shutdown the engine and only turn on the ignition, the pressure shows about 30 psi. 6minutes later if I turn the ignition ON then the pressure will be back to normal 0 psi.

Does anybody else have these readings when the ignition is ON but engine is OFF after freeway driving?

It should read 0 psi at that point I think since there is no oil flowing.

 

Omar,

That sounds like a bad gauge...the dealer should replace under warranty.

I think I read in another thread that the sending unit sensor could also be affected by heat, which might explain the creep...another warrantied item.

Disclaimer: assuming no mechanical or electrical modifications have been made and the oil fill level is within range.

 

Everybody's cars are going to Blow Up! (just kidding) (hope bad karma dont come my way) .....Anyway good luck to everybody on the PSI problem.

 

I changed the pressure sensor and the problem is now gone. I think that the sensor may have been damaged because of overheating problems I had earlier which were due to air in my cooling system.

Just a note. If anyone is draining and refilling their radiator make sure to remove the air relief plug on the heater hose while refilling the radiator. I learnt this the hard way.

Thanks.

 

About 2 months ago I noticed that my oil pressure gauge was only reading right below 30 (which is normal). But under accleration it wouldn't go past 60. I immediately took it into the dealer and got and oil change thinking that I was low on oil. After doing an oil change everything was fine and the pressure was good. Now after 2 months and about 2200 miles it's doin it again. At idle it sits right below 30psi however under hard acceleration it doesn't go above 60 (or even to 60).

If there was a problem with the oil pressure wouldn't the oil light come on? Would it come on for the pressure or oil level? Would the CEL come on if there was a problem? I'm going to the dealer today to have an oil changed and making an appoitment to have the check the pressure sending unit.

Anyone else have this problem?

I usually always shift at high RPM's. Could this have anything to do with the bypass valve opening on the oil filter and causing oil to come out?

 

I have a problem with my Z is that when the RPM at idle speed, the oil pressure go pass the max 120psi. When I accelerate to 5000 RPM, the oil pressure just stay pass the max 120 psi. Anyone know what the problem is? Is it the pressure sending unit malfunction or what.

Any opinion will be helpful. Thanks

 

looks like either sensor or the gauge has gone way down south, take it to the dealer, good luck!!!

 

Thanks kwelii, has anyone else know what cause the sensor or the gauge malfunction??

 

I am taking my car into the dealership tommorow to have the gauges looked at. I have noticed that I am running at almost 0 psi at idle. When I accelerate everything looks normal, except at idle. It is about .1 mm from the part that would hold the needle up when the car is not on, definitely not normal. Also during hard braking in neutral, the oil pressure light will come on in the dash. I checked the oil level, and it is good, so I am guessing that it is a sensor issue? I will keep you updated, lates.

 

Thanks

 

I bring the car to the dealer ship today. They said my aftermarket K&N oil filter casue the problem, but they do not know why it happen. They are going to order the pressure sending unit these day, and will be replace it when it arrived.

 

After having the oil problems I decided to send out an oil sample to BlackStone Oil Labs to have the oil tested. Below are the results.

 

Dude,

your wear numbers looks pretty good compared to Univ AVG. But your oil has thickened up to 40wt in only 1500 miles? Do you have any VOA numbers?

 

Dude,

your wear numbers looks pretty good compared to Univ AVG. But your oil has thickened up to 40wt in only 1500 miles? Do you have any VOA numbers?

 

What is VOA?