jamsvet

This past weekend, had great oil pressure (idle 35, 6k 70) when oil temp was below 220. Above 220 oil pressure dropped (idle 20, 6k 35) At 260 the 6k oil pressure was about 30.

Car has LG big tank and oil was changed one week ago. Mobile synthetic, recommended weight. Engine temp 225. Oil fill is right on the money.

??????Any thoughts as to why????????

Mr. Gizmo

What did the oil pressure used to be before the LG big Tank?

Those oil temps seem high. Mine is usually in the 175 to 190 range- normal street driving with 90-95 degree temps outside. idle at operating temp oil pressure in the 40lb range.

08zee

Where do you live and what was the ambient temperature?

Your oil temp seems high, unless you were working the car hard.

My 08 Z06 runs around 195-215 degree oil temp when ambient is 90-95 degrees and normal highway/city driving. The highest I've seen my oil temp was 245 while running hard on a road course with 95-98 ambient temp here in north Texas.

1stZ

Oil temp is a bit high. Assuming you were in the track working the car hard w/ambient temp above 90*+, then IMO, I's say that both oil temp & pressure are within range. Oil pressure at idle while oil temp is at 260ish, I wish the oil pressure to be a little higher but I believe it is within range.

jmorgan07z06

Mine runs 65 PSI and 175 degrees under normal driving conditions but directly comming off of the track after a 25min session oil pressure drops on average to around 27 PSI at 256 degrees.

sleeplessinseattle

While at Texas World doing a HDE with The Drivers Edge I continue to see oil temps at around 260-270 degrees and my pressure drops to 25-30 lbs. I am told that it should not be a problem but I will know for sure soon. While causally drive home from work one day the timing chain broke, which in turn broke off a value, which in turn pushed the loose value into the block and punched a hole. Soon they will dismantle the crank and inspect the bearings. I will let everyone know at that time if low pressure caused any undue wear on the bearings.

40YRW8

The hotter the oil, the thinner it gets and pumping forces go down and the oil pressure goes down with it. Don't worry about the low oil pressure. Our really good synthetic oils have extremely good high temp shear strength and that is based on the oil itself and has little to do with the oil pressure. However, 0 oil pressure is a totally different case and I would seriously try to keep the oil temp below 300 just in case.
Gary

rattt g

take your oil filter off cut it open and see if you have any bearing
material in there

MitchAlsup

It is NORMAL for oil to become thinner as it gets hotter. As the oil become thinner it is easier to pump and flows through the passages faster. Since the oil flows faster there will be less pressure.

Up to about 265dF you have little to worry about with any of the modern full sunthetics in recommended weights. Between 265dF and 285dF you should start to worry. After 285dF you should adopt a save the engine approach to your driving.

If you continually see 285dF and higher in whatever driving situation you put the car in, an oil cooler or a bigger oil cooler (or still bigger with fans) is better than a thicker oil.

jamsvet

I've got the bigger Harrrison radiator and yes, I was working the engine hard. On the street the temp never gets over 150- 190 for the oil. Working hard, 80 degrees, it got up to about 250. As soon as I let it cool down, the pressure comes right back up. I just don't want to damage anything.

Just drove home about 350 miles on the same oil . Pressure was perfect. Oil temp was about 150 degrees

jlvink66

I have a 2006 Z with about 20K miles and my cold pressures are about the same as yours. I would be a little worried about your hot oil pressures though.

I was on a road course last weekend and my oil temps got to 280F and my oil pressures were 10psi @ idle and 35psi @ 3,000RPM. The general rule of thumb for adequate protection is 10psi/1,000RPM. I'm not real happy with my idle pressures but the pressures seem to be OK at higher RPM's. You might want to consider a heavier weight oil if you haven't already done so. If you don't have enough oil pressure at higher RPMs, you can't keep that crank off the journal bearings. I am close to switching to Redline 5w40 to get that extra protection at higher temps. If heavier weight oil doesn't get you those pressures I would consider freshening up your bearings before it's too late.

John

Painrace

Go to 20W50 oil NOW! You will lose a small amount of fuel mileage but you may save your motor. You should not be on a track with 5W30 oil in my opinion!

Jim

tjwong

I have been advising my customers that are running the HPDE events to run M1 15/50 or simalar weights.

IMHO it is on the low side. Most Zs coming into my shop have idle pressure of around 40+, during a WOT dyno run they will have pressures exceeding 75 PSI with many nearly pegging the oil pressure gauge during a WOT run. I am not getting the oil temps past 200 when performing dyno tests, hence the higer pressures, but it does seem to me that at 6k your pressure at 30 seems a bit low. What is it now during normal driving with temps below 200?

My personal car is one of those also on the low side. On cold start at idle its at 60 PSI, and will easily go to 70+ when reving the engine up to 3000+, once hot with oil temps at 200 degs, the idle pressure drops to 20 to 25, and at higher engine speeds the pressures will get up to maybe 60 PSI.

0Anthony @ LGMotorsports

Completely agree!


By the way.....it has OUR tank in it, or an LPE?


Either way oil capacity should not change pressure, but it can effect temperature. You want to use as thin of an oil as you can get away with, but remember pressure is key #1. If you can not maintain that then go thicker until you can.

obzidian

Right, I've read on here that when tracking the car, you should move up to a heavier oil.

But the higher the temp the thinner it will get. My pressure has dropped to about 20psi with the engine running hot. FWTW, my average oil pressure psi levels have dropped since switching over to Royal Purple 5w30.

Radguy

Wouldn't an oil with a wider viscosity range such as a 0W50 be a better choice than a 20W50 or a 15W50? This way, oil flows well at cold temps but retains higher viscosty at higher temps. Mobil is coming out with a racing oil that is a 0W50 viscosity, supposedly next month.

To me this would be more advantageous especially for those living in more northern locations. If this is incorrect, please explain.

Jonathan

obzidian

hmmm... well, I'm no oil expert but would the "heavier" the oil weight the higher the boiling/shear strength be and run heavier with more heat? A lighter oil will then run thinner with more heat.

Radguy

This is how I understand it. You want an oil that flows well at cold temps especially at start-up, hence a 5W or 0W weight. This is less of an issue in southern climates where it gets really hot in summer.

You want an oil that maintains pressure and lubrication when hot. For street use the recommended wieght is the W30. As you run hotter, i.e. at the track, you have to go to a heavier oil like a W40 or W50. You have to optimise this to maintain oil pressure with a thicker oil, but generate the least amount of heat with a thinner oil.

So, you start with a change from the recommended 5W30 to a 5W40 or a 0W40 to maintain pressure at the track with minimum heat increase. If you still see a pressure drop with the 40 weight oil, you would then change to a 5W50 or 0W50 oil to maintain pressure at the expense of some increased heat.

A 15W50 or a 20W50 would mean a little less lubrication at initial start-up in colder temps.

Does this make sense or am I completely wrong?

I would like some feedback from people in the know. Up to now, my wife and I have done 22 HPDE's using the standard 5W30 Mobil1 on street tires. This summer, we'll be getting more serious with slicks, so I'd like to make the correct change in oil weight.

Jonathan

0Anthony @ LGMotorsports

Jonathan,

You want to run as thin of an oil as you can get away with and maintain pressure. You are correct in that the oil does become thinner as it gets hotter so cooling is one thing to look at as well. 200-260 degree oil temps are pretty normal for a car on the race track so no real worries there...and in some cases can go higher than that. 280-300 degree's is starting to become a problem if it continues like that for long periods of time.

In a perfect world were you can adjust the oil pressure, and control temperature you would heat the oil and water before starting the car, and in the case of say a F1 or Indy car completely circulate the oil and water while it warms before start up. Then adjust to the pressure you need once it is at temperature via an external regulator. Then you can get by with just about any oil weight that you wanted to use.

The thicker oils do tend to take the heat a bit more because they do start off thicker and can generally just take more heat. One thing to think about also is a thicker oil will also generally generate more heat as well because it takes more friction just to pump it through the engine.

Katech_Zach

Cut that oil filter open before you go racing again. 30psi @ 6000 even at 260 deg, I've got my money on your rod bearings. It's best to get a look at that oil filter before you oil down a track and put speed holes in your block.