AE Haas recommends oil pressure to decide weight

[vincent714028]

I don't have a oil pressure gauge. Can someone recommend me a obd 2, scangauge type device that will show me oil pressure and maybe even oil temp.?

Also, he applies this in his racing chapter. Does this also mean it is usable for street daily drivers?

Lastly, if the rule is 10psi per 1000 rpm, then how does he conclude that the gauge should read 75psi at 6000 rpm instead of 60psi?

Thank you.

 

[hate2work]

Vincent, I recommend your owner's manual to decide what grade of oil to run. That system has not failed me in 35+ years of driving.

Don't overthink this, scanners are good tools, but you don't need a scanner to tell you what oil to use.

 

[musicmanbass]

Also, your scanner can only tell you the oil pressure if your car already has a pressure gauge. (Not necessarily a gauge in your instrument panel, but a variable pressure sensor installed in your oil system) If your car has a pressure SWITCH, you will not get a constant display of your pressure level. Think of it as an on/off switch for a light, versus a fading dimmer that tracks with variable input.

 

[JHZR2]

The spec oil viscosity should be ideal for enduring correct pressure. I've never seen substantial variation between viscosities.

 

[friendly_jacek]

Isn't oil pressure regulated by a bypass? If so, when it drops, it's way too thin.

 

[CATERHAM]

Originally Posted By: musicmanbass
Also, your scanner can only tell you the oil pressure if your car already has a pressure gauge. (Not necessarily a gauge in your instrument panel, but a variable pressure sensor installed in your oil system) If your car has a pressure SWITCH, you will not get a constant display of your pressure level. Think of it as an on/off switch for a light, versus a fading dimmer that tracks with variable input.

Correct, and a factory equipped oil temp' sensor to read oil temp's.

Having said that, yes an oil pressure gauge is invaluable to understanding what's going on with your engine and the viscocity of the engine oil at any given moment when the engine is running. An OP gauge is like having your own on board viscometer.

The 10 psi/1,000 rpm is just a guideline. To know what the actual safe minimum oil pressure spec's are for your engine it can take some research to find out. For some engines it can be as low as 50 psi at elevated rev's (Chevy V8's) or 75 psi @ 5,000 rpm (Porsche).
One place to look for the OP spec's is the workshop manual. Two spec's are usually given, one on idle and another at a specified elevated rpm. These would be conservative minimum spec's with the spec' oil grade.

 

[CATERHAM]

Originally Posted By: friendly_jacek
Isn't oil pressure regulated by a bypass? If so, when it drops, it's way too thin.

Maximum oil pressure is limited by the oil pump by-pass valve but the optimum minimum OP is always comfortably below the by-pass setting.
It's one reason why even the lightest 20wt oil is too heavy in every application until the the oil has thinned out sufficiently by reached at least 75C oil temp's.

 

[expat]

My belief is; Oil pressure (from the pump) ALONE is not enough to prevent metal to metal contact at bearings. This is where oil viscosity and film strength come to play.
Consider, many engines rely on Splash lubrication.

Please feel free to critique this theory.

 

[Doug Hillary]

Hi,
vincent - Theories are somewhat dangerous in general practice. IMO and IME the wisdom is with CATERHAM in this area

Some ongoing research on modifying the SAE J300 range to include three additional viscosities 5, 10 and 15 is in place. This has so far confirmed the need for caution on the HTHS viscosity. Some special lubricants with an HTHS below 2.6cP show promise and these require very advanced additive combinations - some using advanced Mo hybrids

Some Japanese Manufacturers are "warm" to this but ACEA is somewhat cool and see no need to change as I understand it

I expect the Chinese Lubes Industry to jump over their predilection with Grp 1 and 2 lubricants into advanced low viscosity fuel efficient lubricants

Some SAE20 lubricants were tried at the Nurburgring 24hr last year - and continued this year

The Manufacturer's recommendations for OP and viscosity are best observed - gemerally use the lowest viscosity possible for your ambient in normal use

 

[CATERHAM]

Hi Doug,

I heard Honda in particular was interested in establishing a 10 and 15 grade classification based on specific HTHS viscosity ranges.
It would make sense to do the same with all oil grades

 

[Doug Hillary]

Hi,
CATERHAM - I agree. The main driver is fuel efficiency of course but there are other drivability benefits. One detractor is the increasing viscosity as used oil ages - to a large degree however modern lubricants are much better than even a half decade ago

Many "experts" here on BITOG that are "locked into" the more ZDDP and etc the better arguments will have to re-educate themselves. Modern formulation lubricants are great products - especially the latest PAO based synthetics and the "new" Grp 3 synthetic families

The role of the Chinese and their joint venturers should never be underestimated in the emerging Lube technologies. Even their latest emmission standards effective from July 1st are being enforced with a vengeance

 

[Jim Allen]

Doug- Better have your flame suit handy ( : < ) . Challenging the Z-God usually brings out the flame throwers.

vincent- You'll have to install a "real" oil pressure gauge but in order to make full use of it the way you want, you also need oil temp. I think you are more likely to find "real" oil temp readings than oil pressure but I only know my Ford V8 has that (no oil pressure, though). An aftermarket oil pressure gauge is fairly easy to install. Oil temp can be more difficult.

Anyway, I've played this game. I have oil pressure and oil temp instrumentation. Know what I found? The factory viscosity recommendations were about right on. What a concept! Anyone who is operating in more or less "normal" circumstances will find the same thing. If you're operating in extremes of climate (situations that are usually covered in the manual by alternative viscosity choices), working your vehicle particularly hard, or have a tired engine with clearances that have opened up dramatically, there may be some room for tweaking. Otherwise, you'll have a lot of fun and gain a lot of insight learning what was right in front of you the whole time... in the owners manual.

IMO, too many people on BITOG are "married" to the "thick is better" or "thin is better" arguments. It's not that simple and more a "what's right for the situation" argument and IMO, the engine designers have done pretty well with that if you fit within their design parameters. In any case, those of us with minds more open are trending toward this statement:

"As thin as possible, as thick as necessary."

We adapted that from the old Camel Trophy off-road driving credo, "As slow as possible, as fast as necessary."

 

[A_Harman]

The best tool for determining what oil viscosity to run in your engine is the owner's manual.

If you seriously modify your engine and then use it for applications for which it was not intended, then you need to think about changing viscosity.

 

[TFB1]

If you're searching for a oil that will give exactly 10psi increase per 1000 RPMs, you'll likely be searching for the rest of your life, ain't happening... I base this on 45 years of vehicle ownership, probably half having a real pressure gauge added... That said if my engines doesn't idle at least 20-25psi and run 40-50 at 2000-3000, I'm worried about their health...

Most all manufactures list hot oil pressure as 35-60psi @ 2000 RPMs...

 

[TurboJim]

Originally Posted By: A_Harman
The best tool for determining what oil viscosity to run in your engine is the owner's manual.


In some cases the manufacturer revises the recommendations found in the original owners manual - http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2143463&page=1

 

[A_Harman]

Manufacturer's have back-spec'ed in the past to allow 5w20 in their engines that were originally spec'ed for 5w30. Have you ever heard of a manufacturer back-spec'ing to a thicker oil to overcome a wear issue? But the principle is still the same: nobody knows more than the manufacurer about what viscosity their engines require.

 

[Peted]

Originally Posted By: Jim Allen

"As thin as possible, as thick as necessary."

We adapted that from the old Camel Trophy off-road driving credo, "As slow as possible, as fast as necessary."



I have all the Camel Trophy vids saved on YouTube. I miss my modded Disco!!!

 

[mechtech2]

Vince -
That 10 lbs/1000 RPM was only a very rough guide.
Don't pay too much attention to it.

Oil TEMPERATURE is a vital piece of info. I'd much prefer an oil temp gauge than pressure - for sure. Keep it around 195F in the sump.



Dr. Haas' massive articles can be summed up:

Engines can use light oils if they don't get too hot. Get it hot by hard use or racing, and then use a thicker oil.


And my 2 cents:

Engines designed for light oils thrive on them.

 

[Ken2]

Dr. Ali E. Haas is a cosmetic plastic surgeon. He is not a mechanical engineer nor a tribologist.

In his writings that I've read, I haven't seen anything about the action that actually separates the metal parts. It is not oil pressure from the oil pump. In every rotating journal bearing, mains, crank, camshaft, the hydrodynamic wedge of oil that is created by the rotation holds the parts apart, sometimes up to 10,000 psi in the bearing. Oil flow merely makes up for the oil that leaks out the ends of the bearings, and of course, carries away heat and debris. I've operated self-contained oil bath (no pump) bearings with a 30" diameter shaft, 60,000 hp, turning at 95 rpm. The hydrodynamic oil wedge caused by the rotation lifts the solid steel shaft and keeps the journal from touching the babbit bearing shell. No oil flow, no pump, no pressure, just running in an oil sump with 30 wt oil (ISO 100).

http://www.substech.com/dokuwiki/doku.php?id=hydrodynamic_journal_bearing

http://www.machinerylubrication.com/Read/779/journal-bearing-lubrication

There are some non-rotating bearings where the oil pump pressure holds the parts apart...oscillating bearings in wrist pins are one example.

If the oil's film strength is inadequate, under load the oil wedge will break down and the parts will touch and fail. Other things remaining equal, the oil film strength relates to the oil's viscosity.

 

[MJB09SRT8]

Ken2, it sounds like you are talking about an aircraft carrier shaft bearing, just a thought i spent 8 years on one.

Montrose