Interpreting oil pressure vs engine RPM

[Shannow]

In addition to Jetronic's point, and expanding from that, I can get 135C in my 3.8V-6 after ten minutes of sustained 4,000RPM operation (holding in 2 at highway speed/loads).

The oil temperature in the big ends is MUCH hotter than either the bulk oil temperature or the gallery temperature.

 

[Emperors6]

Wouldn't the engine designers know that and calibrate the viscosity needed for that in different parts of the engine, and then they would just look at the oil temperature in the pan/gallery?

 

[Shannow]

Yeah, for sure, but there's a school of thought on BITOG that runs.

The engineers know what they are doing (choosing viscosity)
The engineers set a minimum oil pressure (based on wear limits and their design viscosity).
So I'll drop viscosity as long as I reach their minimum oil pressure.

It's a logical fallacy, as the first two don't make the last true.

I interpreted your initial post as wanting comment/affirmation along those lines, and am trying to give you reasons for that path BEING a logical fallacy.

There are posters wthin the thread who have stated that based on your oil pressure, your oil is too thick...I'm trying to educate the other part of the equation.

 

[Emperors6]

Originally Posted By: Shannow
Yeah, for sure, but there's a school of thought on BITOG that runs.

The engineers know what they are doing (choosing viscosity)
The engineers set a minimum oil pressure (based on wear limits and their design viscosity).
So I'll drop viscosity as long as I reach their minimum oil pressure.

It's a logical fallacy, as the first two don't make the last true.

I interpreted your initial post as wanting comment/affirmation along those lines, and am trying to give you reasons for that path BEING a logical fallacy.

There are posters wthin the thread who have stated that based on your oil pressure, your oil is too thick...I'm trying to educate the other part of the equation.


Ah, I see. I should have been more explicit. I would much prefer running what's recommended, it's just that various people I've talked to (incl. my mechanic) wanted me to go to 15W50 or 10W60 for "track" use (it's not hard core by any measure, since I'm still using street tires and it's not more than 30min per session), but I'm really reluctant due to lack of any evidence of the need. So, I did the next best thing and just switched to Red Line at the recommended viscosity since so many rave about its higher temperature properties.

The only viscosity change I wanted to do, was go lower in winter to 0W30 for when temperatures get below -10F. The manual allows for that in really cold (< -20F) conditions.

Overall, my understanding is that the engine is designed to operate optimally around 210-220F. I just want to make sure it doesn't get too high above that, otherwise I want to stick around 5W30.

I just need to decide what my conditions are for running something thicker like Red Line 0W40.

 

[bobbydavro]

Fuel dilution is your biggest enemy with track usage. Not oil thinning out cause it gets too hot

 

[Emperors6]

Originally Posted By: bobbydavro
Fuel dilution is your biggest enemy with track usage. Not oil thinning out cause it gets too hot


Is there any way to combat it after the fact? I usually do a long 8hr highway drive after my track weekends or is prevention by the way of good additives in the oil is the only way?

 

[userfriendly]

I wouldn't assume that you have fuel dilution, based on a blanket statement.
If you read my "best oil for ATS V thread, I'm thinking out loud.
Shannow and a few others can read my mind through my posts, know where I'm going and why.

His invention of XW-HTHS, throws away the KV100, winter cold start and flow performance; use only as required and concentrate on HTHS.
Extending drain intervals late into winter, an engine oil can lose a W grade, for example; from 15W down to 20W, which is a huge loss in cold performance,
Don't chase VI as HTHS, and especially post permanent shear HTHS go in the opposite direction.

With high VI engine oils like 0W40, typically you will end up with a much higher KV100C to pay for a small HTHS gain.

Post TVL HTHS is the viscosity that floats your engine's plain bearings, thick oils create more heat while providing more protection.

 

[CT8]

Originally Posted By: Emperors6
Hi,

I was wondering if I could some help determining if I chose the correct oil for my summer application. I have switched to Redline 5W30 for the summer (due to track days mostly).

I'm working on my logging setup, but here's some graphs from a 500mile (mostly highway trip). It doesn't look like I meet the 1000rpm/10psi "rule." Any advice?

you have to play around with heavier oils. Hot hot hot oil pressure is what you are going to need as a data point.

 

[Emperors6]

Originally Posted By: CT8
Did you read oil university?

Yah, but a lot of it seemed anecdotal without any engineering behind it. Claims need testing through extensive experimentation.

 

[CT8]

Originally Posted By: Emperors6
Originally Posted By: CT8
Did you read oil university?

Yah, but a lot of it seemed anecdotal without any engineering behind it. Claims need testing through extensive experimentation.
It is rather foolish but I had to come back on the reply. . Hot oil pressure when tracking at the higher RPMs as mentioned is what you want. summer racing and winter starting needs will be different viscosity needs. My last big block boat engine oil pressure was close to 100 psi as 1,500 cold idle RPM and hot oil pressure was about 70 psi rpm at 7,500 running 15w-40 and a bit higher running 20w-50. The only problems over the years were broken valve springs and cam wear which is common. If there are hard core racers that you track with running the same engine talk to them.

 

[A_Harman]

Originally Posted By: Emperors6
Originally Posted By: Shannow
Yeah, for sure, but there's a school of thought on BITOG that runs.

The engineers know what they are doing (choosing viscosity)
The engineers set a minimum oil pressure (based on wear limits and their design viscosity).
So I'll drop viscosity as long as I reach their minimum oil pressure.

It's a logical fallacy, as the first two don't make the last true.

I interpreted your initial post as wanting comment/affirmation along those lines, and am trying to give you reasons for that path BEING a logical fallacy.

There are posters wthin the thread who have stated that based on your oil pressure, your oil is too thick...I'm trying to educate the other part of the equation.


Ah, I see. I should have been more explicit. I would much prefer running what's recommended, it's just that various people I've talked to (incl. my mechanic) wanted me to go to 15W50 or 10W60 for "track" use (it's not hard core by any measure, since I'm still using street tires and it's not more than 30min per session), but I'm really reluctant due to lack of any evidence of the need. So, I did the next best thing and just switched to Red Line at the recommended viscosity since so many rave about its higher temperature properties.

The only viscosity change I wanted to do, was go lower in winter to 0W30 for when temperatures get below -10F. The manual allows for that in really cold (< -20F) conditions.

Overall, my understanding is that the engine is designed to operate optimally around 210-220F. I just want to make sure it doesn't get too high above that, otherwise I want to stick around 5W30.

I just need to decide what my conditions are for running something thicker like Red Line 0W40.


GM has lately started recommending M1 15w50 for the Corvette when running track days. Their recommendation is in the owner's manual, so they must see some benefit in thicker viscosities. And at the very least, "thicker" won't hurt the engine. Contrary to your mechanic, I wouldn't go to 10w60, which will probably turn into 50 or 40 in your engine. Redline 5w30 has an HTHS of 3.7, which is basically the same as M1 0w40, so it will behave like a 40-weight in your engine. And Redline is very shear stable.

I have run Redline 5w30 in my Corvette track car at temperatures up to 315F in the main oil supply gallery, and the engine runs an average oil pressure of 35 psi. It's been running that way for 20 years, and still runs fine. Don't get too fixated on oil pressure, just make sure it is stable.

 

[userfriendly]

In addition to my last post, I would say that KV100C influences oil pressure at operating bulk oil temperature.
The viscosity of the oil in the sump is what the pump sees, but there is a catch.
First is the pressure the pump relief is set to, and secondly, that pump may be a variable volume AND pressure design.
What pressure is the ATS V pump set to, or is it variable displacement?
Does your engine have pressure activated piston cooling jets?
These are all questions that need to be answered before going down the viscosity trail and stepping on a rake in the dark.

 

[Emperors6]

It has piston oil cooling, I don't know if it's pressure activated. Also, according to bulletin PIP4158C it seems to have a set relief valve.

 

[userfriendly]

Piston cooling through a metered nozzle is a function of pressure and density.
An extreme contrast of that for visualization, would be blowing air at low pressure on a hot surface, to water at high pressure.

Do you agree with this statement?
Thicker oil will improve piston cooling.

What is missing from the statement?

If a thinner oil reduces pressure, would piston cooling be compromised?

 

[virginoil]

Originally Posted By: Emperors6
Hi,

I was wondering if I could some help determining if I chose the correct oil for my summer application............


Could not resist this response.

Follow the recommendations in the Owners Manual and it will help limit the wondering.

Are there not BITOG opinions as an approved alternative in the Owners Manual.

 

[bobbydavro]

Originally Posted By: Emperors6
Originally Posted By: bobbydavro
Fuel dilution is your biggest enemy with track usage. Not oil thinning out cause it gets too hot


Is there any way to combat it after the fact? I usually do a long 8hr highway drive after my track weekends or is prevention by the way of good additives in the oil is the only way?


It will boil off on a highway. Under hard use the fuel dilution thins our ANY oil, no matter the grade. This depends on the hardware and the fact you are being recommended a thicker grade by the OEM is supporting this.

A 12.9 cSt oil thins out to 10.2 cSt with just 9% dilution. This dilution was from 250miles of track usage. once you boil the fuel off the Kv100 was back up to 12.8cSt.

This is the key reason for thicker oils for track usage - to allow the correct viscosity characteristics when the fuel is diluted.

Not using a 60grad cause it thins to a 40 or 50 seems a rather silly argument to me. The fact it is thinning is evidence as to why it needs to be thick in the first place.

 

[buster]

Quote:
This is the key reason for thicker oils for track usage - to allow the correct viscosity characteristics when the fuel is diluted.


That's very true. I read that years ago from a Motul guy who said they recommended 15w50 for endurance racing due to fuel dilution over the course of the race.

 

[A_Harman]

Originally Posted By: Emperors6
Originally Posted By: Shannow
Yeah, for sure, but there's a school of thought on BITOG that runs.

The engineers know what they are doing (choosing viscosity)
The engineers set a minimum oil pressure (based on wear limits and their design viscosity).
So I'll drop viscosity as long as I reach their minimum oil pressure.

It's a logical fallacy, as the first two don't make the last true.

I interpreted your initial post as wanting comment/affirmation along those lines, and am trying to give you reasons for that path BEING a logical fallacy.

There are posters wthin the thread who have stated that based on your oil pressure, your oil is too thick...I'm trying to educate the other part of the equation.


Ah, I see. I should have been more explicit. I would much prefer running what's recommended, it's just that various people I've talked to (incl. my mechanic) wanted me to go to 15W50 or 10W60 for "track" use (it's not hard core by any measure, since I'm still using street tires and it's not more than 30min per session), but I'm really reluctant due to lack of any evidence of the need. So, I did the next best thing and just switched to Red Line at the recommended viscosity since so many rave about its higher temperature properties.

The only viscosity change I wanted to do, was go lower in winter to 0W30 for when temperatures get below -10F. The manual allows for that in really cold (< -20F) conditions.

Overall, my understanding is that the engine is designed to operate optimally around 210-220F. I just want to make sure it doesn't get too high above that, otherwise I want to stick around 5W30.

I just need to decide what my conditions are for running something thicker like Red Line 0W40.


And here's another thread discussing thicker oils in Gen V engines for track use:

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4094665/1

 

[A_Harman]

Originally Posted By: bobbydavro
Originally Posted By: Emperors6
Originally Posted By: bobbydavro
Fuel dilution is your biggest enemy with track usage. Not oil thinning out cause it gets too hot


Is there any way to combat it after the fact? I usually do a long 8hr highway drive after my track weekends or is prevention by the way of good additives in the oil is the only way?


It will boil off on a highway. Under hard use the fuel dilution thins our ANY oil, no matter the grade. This depends on the hardware and the fact you are being recommended a thicker grade by the OEM is supporting this.

A 12.9 cSt oil thins out to 10.2 cSt with just 9% dilution. This dilution was from 250miles of track usage. once you boil the fuel off the Kv100 was back up to 12.8cSt.

This is the key reason for thicker oils for track usage - to allow the correct viscosity characteristics when the fuel is diluted.

Not using a 60grad cause it thins to a 40 or 50 seems a rather silly argument to me. The fact it is thinning is evidence as to why it needs to be thick in the first place.


I was talking about permanent viscosity loss due to shearing on an oil with as wide a viscosity spread as a 10w60. The Motorcraft 5w50 that Ford recommends for performance applications is notorious for shearing out of grade, sometimes two grades if it is run hard enough.

Fuel dilution is another matter. If an engine has 9% fuel dilution from running 250 miles on track, I think that it has a problem with poor fuel vaporization or excessively rich mixture.

 

[bobbydavro]

They don't only shear out of grade. They simply get diluted. Fuel has a bigger impact on thicker viscosities