If your Pressure is Fine, can you go down a grade?

[HangerHarley]

I just had a thought. If i get my Oil Pressure tested and it reads that its fine, or too high, should i just stick with this 10W-40 MaxLife, and be done with it?

I have the 94 Probe that runs well but drinks a little Oil, with unknown amount of Sludge.

If my Oil Pressure tests out around 60Psi or so driving down the road, can i stick with 10W-40 and be done with it?

And let the HM Oil clean whatever it will? Is MaxLife 10W-40 good at cleaning things up, im asking specifically about Rings, with or without Moly like the infamous MoS2?

If its that simple, im relieved.

?

 

[mechtech2]

Where does the "go down a grade" part come into play?
From a 10-40 to a 10-40?

 

[HangerHarley]

Well, i should have said "Keep it 10W-40" if a 50-wt. gives it to much pressure, as determined by a Mechanical gauge.

 

[Gary Allan]

Complicated topic, Harley. I don't think that there's any true pressure requirement in the engine, per se~. Bearings need a given "minimum volume at minimum visc" to account for side leakage and heat. ..the rest just requires enough of a refresh rate to keep an oil film between the rubbing parts.

Pressure is a side effect ..sorta. You pick up some stuff through osmosis here.

 

[Steve S]

Where do you get these ideas .I think I know from the verbage used.

 

[HangerHarley]

Originally Posted By: Steve S
Where do you get these ideas. I think I know from the verbage used.

What if i told you i had a Gauge installed in the engine, and it reads close to 80Psi?

This is why i talk of perhaps going down a grade, however some say the Engine may "Slap itself to death."

I dont know where "Normal" pressure would be at 2500RPM while driving, but id assume its around 60psi. Not 80psi..

 

[Boss302fan]

Maxlife has a good amount of moly and also cleans very well. I would just stay with what you currently are using.

 

[Gary Allan]

Quote:
What if i told you i had a Gauge installed in the engine, and it reads close to 80Psi?


Depending on how you felt about it, I'd either congratulate you or give you my sympathies.

All kidding aside, have we determined what is the minimum acceptable visc for this engine? I know it's allegedly tired and subject to some consumption, but does anything weird happen with a common 30 grade? If there's no rumbling or ticking ..or knocking ..and JUST consumption, then a movement up in viscosity would be a consideration to see if it reduced it. I'd only do this if consumption was excessive ..or rather that the change in visc substantially altered it. Otherwise, consumption without other negative side effects is nothing to fear or compensate for.


What's your hot idle pressure with your current (what's in there now?) oil, Harley? How long does it hang pegged out at (near) 80psi?

 

[Jim Allen]

I would only use the pressure to evaluate wear (internal bearing clearances, etc) and, if necessary, go up a grade to match the factory engine oil pressure specs. Based on my experience, that would seldom be demonstrably necessary.

I forget.. was the '94 Proble the original version with the 3.0L pushrod V6 (we had one... great car!), or was it the later one with the 2.5L V6. If the 3.0L, I have a manual that lists the normal hot oil pressure as 55-70 psi at 2500 rpm, hot engine with 5W30 oil. Later specs for that engine in a Ranger shows 40-60 psi @ 2500 hot with 5W20 oil. If your oil pressure meets these specs with the correct oil, I submit you are OK on the viscosity, at least in terms of the bottom end. 80 psi seems a little higher than necessary, so were I you, I would scale back to a HM 5W30 or 10W30. If you do, would appreciate hearing back, would appreciate hearing how the pressure changes.

 

[HangerHarley]

Originally Posted By: Jim Allen
I would only use the pressure to evaluate wear (internal bearing clearances, etc) and, if necessary, go up a grade to match the factory engine oil pressure specs. Based on my experience, that would seldom be demonstrably necessary.

I forget.. was the '94 Proble the original version with the 3.0L pushrod V6 (we had one... great car!), or was it the later one with the 2.5L V6. If the 3.0L, I have a manual that lists the normal hot oil pressure as 55-70 psi at 2500 rpm, hot engine with 5W30 oil. Later specs for that engine in a Ranger shows 40-60 psi @ 2500 hot with 5W20 oil. If your oil pressure meets these specs with the correct oil, I submit you are OK on the viscosity, at least in terms of the bottom end. 80 psi seems a little higher than necessary, so were I you, I would scale back to a HM 5W30 or 10W30. If you do, would appreciate hearing back, would appreciate hearing how the pressure changes.


Well, its the 2.5, and thanks for the Ratings!

It will be a few weeks before my OC, however I think i have an idea of how to handle the Viscosity. Thanks Jim!

 

[CATERHAM]

You're on the right track.

Oil pressure correlates directly with the oil's viscosity which of course is temperature dependant.
Assuming your engine's spec' oil pressure is 60 psi at max' rev's then the lightest oil that provides that is all you need when the oil is the hottest.

If you're seeing oil pressure of 80 psi with the oil as hot as you're likely to see, then very likely you're running an oil thicker than necessary and I'd try a grade lighter.

BTW, just so you know oil pressure correlates closely with the HTHS vis spec' more so than with the 100C k'vis spec'.

I had the same observation a car of mine and I dropped down from the spec' 5W-50 to a 0W-20. I didn't know the reason why my oil pressure was so high until I installed a oil temp' gauge. The oil temp's rarely got above 80C.

 

[HTSS_TR]

Originally Posted By: CATERHAM

I had the same observation a car of mine and I dropped down from the spec' 5W-50 to a 0W-20. I didn't know the reason why my oil pressure was so high until I installed a oil temp' gauge. The oil temp's rarely got above 80C.


I thought that I was crazy in dropping 2 grades from the spec'd 0W40 to xW20 in my '00 E430.

I think oil temperature gauge is essential in high performance cars, specially when you want to try thinner oil to match your driving style. If your spec'd oil is rarely above 100C you can safely use 1 grade light oil.

 

[HangerHarley]

IS there a way to determine oil TEMP and not Oil PRESSURE?

Maybe my Filter is just plugged up.

 

[mechtech2]

Originally Posted By: CATERHAM
You're on the right track.

Oil pressure correlates directly with the oil's viscosity which of course is temperature dependant.
Assuming your engine's spec' oil pressure is 60 psi at max' rev's then the lightest oil that provides that is all you need when the oil is the hottest.

If you're seeing oil pressure of 80 psi with the oil as hot as you're likely to see, then very likely you're running an oil thicker than necessary and I'd try a grade lighter.

BTW, just so you know oil pressure correlates closely with the HTHS vis spec' more so than with the 100C k'vis spec'.

I had the same observation a car of mine and I dropped down from the spec' 5W-50 to a 0W-20. I didn't know the reason why my oil pressure was so high until I installed a oil temp' gauge. The oil temp's rarely got above 80C.


Pretty good post.
We also have to remember that a thinner oil cools better, and often runs cooler than thicker oils in an engine. This keps it's viscosity up.

 

[Shannow]

Originally Posted By: CATERHAM
You're on the right track.

Oil pressure correlates directly with the oil's viscosity which of course is temperature dependant.
Assuming your engine's spec' oil pressure is 60 psi at max' rev's then the lightest oil that provides that is all you need when the oil is the hottest.


Except it's not the oil pressure keeping the bearings apart, and it doesn't really correlate with the viscosity within the bearing, and nor does the bulk oil temperature tell you what's happening in each individual bearing, each of which will have a higher oil temperature temperature than that shown on your sumpgauge, and be running significantly thinner oil than the supply viscosity.

Originally Posted By: CATERHAM
BTW, just so you know oil pressure correlates closely with the HTHS vis spec' more so than with the 100C k'vis spec'.


Not quite sure how you can make that claim, as the oil velocity through the galleries isn't flowing at a shear rate (nor temperature) that correlate with that.

I can understand bearing protection being better correlated to HTHS.

Originally Posted By: CATERHAM
I had the same observation a car of mine and I dropped down from the spec' 5W-50 to a 0W-20. I didn't know the reason why my oil pressure was so high until I installed a oil temp' gauge. The oil temp's rarely got above 80C.


And the bearings were being lubricated with an oil pretty close to the 20 part of the 0W-20.

Oil films, and safety margins were definitely lower than with the 5W-50, although the 5W-50 would have run warmer, I think.

 

[demarpaint]

Originally Posted By: mechtech2
Originally Posted By: CATERHAM
You're on the right track.

Oil pressure correlates directly with the oil's viscosity which of course is temperature dependant.
Assuming your engine's spec' oil pressure is 60 psi at max' rev's then the lightest oil that provides that is all you need when the oil is the hottest.

If you're seeing oil pressure of 80 psi with the oil as hot as you're likely to see, then very likely you're running an oil thicker than necessary and I'd try a grade lighter.

BTW, just so you know oil pressure correlates closely with the HTHS vis spec' more so than with the 100C k'vis spec'.

I had the same observation a car of mine and I dropped down from the spec' 5W-50 to a 0W-20. I didn't know the reason why my oil pressure was so high until I installed a oil temp' gauge. The oil temp's rarely got above 80C.


Pretty good post.
We also have to remember that a thinner oil cools better, and often runs cooler than thicker oils in an engine. This keps it's viscosity up.


2 good posts. A Probe engine is not a high performance engine, and a 30 grade oil is all that engine needs, unless there is something wrong with it. Reading thru the OP's posts I think he favors thicker oils. If it is the slight oil consumption you are trying to eliminate using a thicker oil might increase the oil use. Shell did a study on oil viscosities. They said if it is ring wear, namely the top ring that is causing oil use, 5W20 actually decreased oil use vs. a 10W40 oil. It goes against what many of us were told but it is spelled out in their report. It's been a while since I've read it but there are a few guys on the site that have seen it and can probably elaborate.

 

[beanoil]

[/quote]

A Probe engine is not a high performance engine, and a 30 grade oil is all that engine needs, unless there is something wrong with it. [/quote]
While I agree a 30 weight should be fine, don't overlook the fact that the US spec engine in the Probe is a detuned Mazda KLZE, quite the powerplant for it's size...
The Mazda K-series automobile engine is a short stroke, 60° V6 24-valve with belt-driven DOHC and aluminum-alloy cylinder heads and block. Their displacements range from a tiny 1.8 L to 2.5 L. They all use a 27-degree DOHC valvetrain with directly actuated hydraulic (HLA) bucket lifters. The K-series also feature a highly-rigid, all-aluminum split-crankcase engine block design with 4 & 6 bolts for each main journal, internally balanced forged crankshaft with long, lightweight forged carbon steel connecting rods. They were designed to be as compact as possible for short-hood front-wheel drive applications.

 

[HangerHarley]

Originally Posted By: beanoil



A Probe engine is not a high performance engine, and a 30 grade oil is all that engine needs, unless there is something wrong with it. [/quote]
While I agree a 30 weight should be fine, don't overlook the fact that the US spec engine in the Probe is a detuned Mazda KLZE, quite the powerplant for it's size...
The Mazda K-series automobile engine is a short stroke, 60° V6 24-valve with belt-driven DOHC and aluminum-alloy cylinder heads and block. Their displacements range from a tiny 1.8 L to 2.5 L. They all use a 27-degree DOHC valvetrain with directly actuated hydraulic (HLA) bucket lifters. The K-series also feature a highly-rigid, all-aluminum split-crankcase engine block design with 4 & 6 bolts for each main journal, internally balanced forged crankshaft with long, lightweight forged carbon steel connecting rods. They were designed to be as compact as possible for short-hood front-wheel drive applications. [/quote]

Yah. Mine has a Chip in it too, and some of the Ricer stuff.

Idk. Maybe ill keep it 10W-40 and do an Auto-Rx. By the end of that Rinse phase it will be winter, and Castrol SYNTEC 5W-50, which is a "thin 50" it has to be, will enter the engine at that time.

And there it will stay...

.. So maybe i DID choose an Oil!

(Oh, and regarding the Syntec. If it is ALMOST a Synthetic, but not quite, thats fine. Most of the time, id be afraid to run a Synthetic anyway, so that too suits the bill.) Why, you ask?

Three reasons:

1) Conventional advice about Synthetics and cars with around 200,000 miles.. It has th epossibility to not work as you desire. (PP Strike 1)
2) The engine came with Dino, so along the way its been used, abused, and mutilated, with certain God-knows-what done to it, maybe even some Overheats

So.. A High0Quality Oil is desired, Synthetic and Conventional terms not applying. PP Strike 2
3) AVALIABLILTY, and characteristics of Cold Flow, Hot Viscosity, and HT/HS.
Winner: Castrol "It Might be Synthetic it Might Not, Who Cares" Syntec 5W-50. AFTER ARX. (Supertech 10W-40 used during ARX. If not, Delo 400 15w40. Shoot, forgot all about Delo 400 at WM.

OK, Delo 400 15w40 OR ST 10W-40 (Ill flip a coin) for ARX, then Xastrol Syntec 5W-50 after that, first application will be in the Winter months when it comes time to start wearing the Coats and enjoying the Fall weather, before the Freezing starts.

 

[demarpaint]

I guess I look at High Performance engines differently. I'm not knocking the Probe engine, guys, so don't get me wrong. I still think a 5W30 or 10w30 would work fine in that application. We've used 30 grade oils in worked Ford 302's, 351's, and Chevy 350 HP applications without issue.

 

[CATERHAM]

Originally Posted By: HangerHarley
IS there a way to determine oil TEMP and not Oil PRESSURE?

Maybe my Filter is just plugged up.


Oil pressure is the bottom line. To determine oil temp's you'll need to get an oil temp' gauge and sensor. There are single gauges that will measure both.