Oxidation: Solvent vs hyrotreated base oils

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wemay

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The Importance of Oil Oxidation Stability

http://www.machinerylubrication.com/Read/28966/oil-oxidation-stability

There is a little controversy concerning the oxidation stability of natural mineral base oils as determined by the refining method. There is one school of thought that suggests that hydrotreated base stocks have superior oxidation resistance and thermal stability than does solvent-refined base oil.

This is based on the misconception that since hydrotreating removes all of the potentially undesirable compounds, the base oil tends to automatically reduce deposit-forming tendencies and thereby will better resist oxidation. However, removing all of the compounds considered undesirable can in fact be detrimental.

Solvent refining results in the production of base oils, which retain some sulfur compounds that are natural antioxidants. These base oils retain a natural ability to prevent oxidation, while hydrotreated base oils must be further fortified with antioxidants in order to maintain thermal and oxidation stability. Once the antioxidants are weakened or depleted, oxidation of some hydrotreated oils can occur very rapidly.

Severely hydrotreated base oils also have poor solubility characteristics. Without proper formulation, additives may not remain suspended, and some additive drop out could occur.
 
I've heard the "Dino" oils do have better solvency, maybe synthetic has different detergents to counteract this?
 
Originally Posted By: zach1900
I've heard the "Dino" oils do have better solvency, maybe synthetic has different detergents to counteract this?


Yes I would say that's true, generally the higher tier oils in any brands lineup has a more potent additive package than the same brands conventional. Higher calcium, moly, Boron, magnesium tend to showcase up if you lookin at the VOAs.
 
Originally Posted By: Shannow
wemay,
I've been bitten by exactly that.

The GrII is more oxidation resistant, but the lack of polar "contaminants" make it weak as far as keeping the oxidation byproducts in solution.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/736251/1

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=964078

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2855387

http://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/printthread/Board/17/main/41015/type/thread


This stuff gets more interesting by the day. Lol
 
I read through a lot of those links as well and have come to the conclusion that there really is no...conclusion. Whatever side you're on, an intelligent argument can be made for it based on theories published in Machinery Lubrication, Lubrizol and other respected institutions. Wait until GF-6A and GF-6B get here, Bitog will never become stale with so much constant change in the industry.

The one thing that appears to have consensus:

'...polyalphaolefins (PAO), have inherently better oxidation stability than do mineral oils. This improved oxidation stability accounts for the slightly higher operating temperatures that these synthetic oils can accommodate.'

So better, but only slightly in this respect.
 
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Originally Posted By: Shannow
wemay,
next research "carrier".

PAO is pretty not good at holding products in solution also.


I just got a headache.
 
wemay,
PAO is non-polar as well, so is not a very good solvent for things like varnish, and even in the early days additive packs.

Was one of the reasons for the M1 haters in the early BITOG days when the additives were introduced to the GrIV oil in a GrI "carrier"...making M1 a "semi" during arguments back in the day.

It's all a balancing act...III and IV don't hold additives/oxidation byproducts as readily as GrI...but produce much less of them.

GrII (in steam turbines), performs great in regular oxidation tests, and then crashes, while GrI gets worse and worse, but gives plenty of warning.
 
Esters are, on the other hand, polar. Not sure about AN's. But I imagine both are used in the Mobil products for various reasons and perhaps one of those is to help with additive solubility.
 
True OVERKILL, Bruce381 (another great MIA member) summarised it here

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=145752

Originally Posted By: bruce381
depends, they both have drawbacks and are used in combination to balance out the best.

.........................PAO....ESTER
Additive solubility......bad....good
VI.......................good...medium
Hydrolitic stability.....good...bad
low/high vis grades......good...medium
cost.....................low....high

other diferences but you get the idea.
bruce
 
10.gif
OVERKILL, glad you liked it...I knew the discussion had been had, and was stoked to have found it, back in the days of BITOG facts and data rather than factless posits.
 
Originally Posted By: Shannow
10.gif
OVERKILL, glad you liked it...I knew the discussion had been had, and was stoked to have found it, back in the days of BITOG facts and data rather than factless posits.


Good stuff guys...
 
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