Temperature of oil breakdown?

[Jojo]

I realize this topic has been beat to death but I couldn't find what I was looking for.
I have search fairly extensively last night and this morning. So if I missed this information somewhere on this site please direct me to it Thanks.
I'll be installing an oil temp gauge for the use at track days.
I have an Acura Integra and I just installed a Integra Type-R oil cooler. Little did I know that the cooler is actually cooled with coolant rather than an oil to air type of cooler. The adapter is a sandwich type but the inlet and outlet hook up to the rear coolant pipe (connecting pipe). Coolant being cooler than the oil and having a radiator seems pretty smart to me. Any thoughts on this?
After reading alot of the threads on here (great information) I now know that oil oxidizes after a certain temperature but at what point (temperature) does it start to break down and not protect the engines parts from damage?
I am currently using AMSoil.

[ February 06, 2005, 03:23 PM: Message edited by: Jojo ]

 

[mountravlr]

Some of the synthetics are rated at around 450 degrees (flash point) and 490 degrees (fire point). Temps this high over extended time will degrade the oil.

 

[ruking77]

Right! All you really have to do is to go to each individual oil specification sheet to get each oils specifics. Also the additional problem can be seen on, for example; Toyota "sludge monster" engines! The engines really need to be engineered and tested so that the internal surface areas operate within the engine oils (conventional or synthetic) as almost any engine operating out of parameters will "cook" the oil. This will of course increase the chances of sludge formation.

 

[Jojo]

Thanks for your responses.
The flash and fire points don't really tell the tale of when the oil stops providing adequate lube for the parts. Just when they absolutely fail. If my oil gets anywhere near that point, I have other problems....

 

[Mickey_M]

quote:

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Jojo:
.... After reading alot of the threads on here (great information) I now know that oil oxidizes after a certain temperature but at what point (temperature) does it start to break down and not protect the engines parts from damage? ....

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That depends on the motor oil.

A temperature gauge will give you a reading at some point in the system where its sensor is.

The oil in the engine will be hotter or cooler depending on whether it's on the cylinder wall (very hot), cylinder head (pretty darned hot), crankcase (not too bad).

Overall the oil is going to be, on average, well below the flash and fire points. If it wasn't you'd have gaskets melting and valves burning, not to mention piston crowns burning.

So, think of it more in terms of a small amount of degradation slowly accumulating until motor oil can't deal with it anymore, at which point it's depleted.

 

[XS650]

Several years ago a Mobil Oil lube engineer told me something that was real obvious once he told me

How much the oil gets whipped around in the crankcase has a definite effect on how fast it degrades. While it is getting flung around in dropplet and spray form in what passes for an atmosphere in the crankcase it degrades faster. That's because so much more surface area is exposed to the atmosphere in the crankcase when the oil is in droplet form and flying around.

He also said that one of the lesser known benefits of a windage tray in some engines is that it improves oil life a bit because the oil isn't flung around as much.

 

[Razl]

quote:

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That's because so much more surface area is exposed to the atmosphere in the crankcase when the oil is in droplet form and flying around.

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I see the physics but what is it in the crancase atmoshere that's going to age the oil faster? I don't get it.

 

[MolaKule]

Good point.

Oxidation involves BOTH heat and oxygen. Heat an oil high enough and then subject it to turbulent air, and oxygen gets "whipped" into the oil.

Of course, oxidation inhibitors reduce that effect so the oil lasts longer.

 

[Jay]

quote:

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Originally posted by Jojo:
...Little did I know that the cooler is actually cooled with coolant rather than an oil to air type of cooler. The adapter is a sandwich type but the inlet and outlet hook up to the rear coolant pipe (connecting pipe). Coolant being cooler than the oil and having a radiator seems pretty smart to me. Any thoughts on this?...

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I like this style of "cooler" because it serves a dual function. It heats the oil when it's cold as well as cools the oil, plus the cooling is somewhat thermostatically controlled.

 

[pitzel]

quote:

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Originally posted by MolaKule:
Good point.

Oxidation involves BOTH heat and oxygen. Heat an oil high enough and then subject it to turbulent air, and oxygen gets "whipped" into the oil.

Of course, oxidation inhibitors reduce that effect so the oil lasts longer.

---

Can we generally consider oil oxidation as an Arrhenius-type process, ie: governed by the Arrhenius relationship, which uses temperature as its main variable?

 

[TC]

"...at what point (temperature) does it start to break down and not protect the engines parts from damage?"

"Conventional oils will tolerate engine oil sump temperatures of up to 250 to as much as 275 degrees F without difficulty. According to Quaker State engineer Mark Farner, oils like Quaker State's full synthetics can easily withstand sump temperatures in excess of 300 degrees F, and he says that some oval track race teams are experimenting with temperatures as high as 350 degrees F. For a typical wet-sump engine, 300 degrees F is still extremely hot, but Farner says that synthetics, because of their molecular makeup, are better suited to withstand these temperatures. The downside is that additive packages do tend to break down faster in high-temperature environments, so if you plan on running oil temperatures in excess of 300 degrees, this would mean changing the oil after every track event regardless of the mileage. For example, due to the intense frictional heat generated, Britney Spears changes out her lubricant after every 'event,' bootleg videos of which will soon be offered on the Internet."
http://www.carcraft.com/techarticles/116_0409_slip/

 

[Fuelrod]

TC gave you the best answer. You want to keep it below 250 degrees F. 225 is good and 200 even better. Synthetics can take more heat (they claim) before oxidizing, but other parts of your engine can not....

Fun test. Pour a quart of your favorite motor oil in a sauce pan and heat it up. A fry thermometer will tell you where you stand. Observe when it starts smoking. (Around 300?) That's WAY to hot!

 

[John K]

I suspect this is a very involved subject, and that besides the oil degradation itself the various additives might have their own limits, and in turn having an effect on the oil. Good luck.

 

[MolaKule]

quote:

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The flash and fire points don't really tell the tale of when the oil stops providing adequate lube for the parts.

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You are now discussing two different subjects.

The oil stops lubricating when the film gets too thin. This happens when the temp goes too high and neither the base oil film nor the VII's can keep the thinning in check.

The oil degrades over time, as Mickey-M stated so well. That's why we have OCI's.

Oil analysis will tell you when the oil is ready for change for your engine/oil combination.

 

[Blue99]

A GF-4 rated oil must pass the Sequence IIIG test, which is a torture test measuring oil thickening, piston deposits, stuck rings & cam lifter wear.

It's run on the GM 3.8L for 100 hrs @ 3600 rpm and 150C (300 deg F). The oil level is checked every 20 hrs & up to 4.6 liters, roughly 5 qts, of make-up oil is allowed.

So, while 300F is a pretty severe test of an oil's volatility, GF-4 oils are expected to survive a pretty healthy dose of this temperature level!

 

[Mickey_M]

quote:

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pitzel:

Can we generally consider oil oxidation as an Arrhenius-type process, ie: governed by the Arrhenius relationship, which uses temperature as its main variable?

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http://www.shodor.org/UNChem/advanced/kin/arrhenius.html

"Common sense and chemical intuition suggest that the higher the temperature, the faster a given chemical reaction will proceed. Quantitatively this relationship between the rate a reaction proceeds and its temperature is determined by the Arrhenius Equation. At higher temperatures, the probability that two molecules will collide is higher. This higher collision rate results in a higher kinetic energy, which has an effect on the activation energy of the reaction. The activation energy is the amount of energy required to ensure that a reaction happens."

The answer is "yes".


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[Al]

Rate of conventional oil oxidation doubles for every 18 degrees F above 150 F