Better base oil (PAO) not necessarily better performance: A study of 5W-40 oils

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This is a Czech study from early 2000s, using fourteen mostly A3/B3 5W-40 oils purchased in 1999.

Interestingly, they determined the base-oil composition, namely the PAO, HC, and ester content of each oil, using chromatography.

Then, they performed an oxidation test based on the standard IP 48 method. They measured the viscosity increase, micro carbon residue, and TAN.

While the results were usually consistent with the expectation that more PAO and less HC lead to slower oil oxidation or a longer oil-change interval, there were exceptions, with some PAO-based oils performing rather poorly and some HC oils performing exceptionally well.

The culprit: antioxidants. If the antioxidants are not well-matched to the base oil or they are in insufficient quantity, you have a short oil life even with the top-quality base oils like PAO.

Moral of the story: Claims of synthetic, PAO, etc., while encouraging, do not necessarily guarantee performance. You still need a good additive package with good antioxidants in generous amounts.

Composition and oxidation stability of SAE 5W-40 engine oils
J. Cerny, M. Pospisil, and G. Sebor, Department of Petroleum Technology and Petrochemistry, Institute of Chemical Technology
I. Vaclavickova and N. Vinklarkova, Koramo a.s.


Note that in this article, synthetic refers to a PAO (API Group IV) base oil and semisynthetic refers to a PAO - HC base-oil blend.

The list of the oils tested with their determined base-oil compositions:

[Linked Image]


Spoiler alert: The article codes the tested oils with letters and does not disclose which letter corresponds to which oil in their test results.
 
today in the $5 a qt price range fake synthetic group III oils have replaced the real synthetics of the past, thank you not castrol when you illegally sold syntec as a synthetic before a ruling allowed it.
 
The way I understand it PAO is a general term. There are a number of different PAO formulations and most PAO based oils are a blend of those formulations. Same with esters.

So this becomes more complicated than the study above. If I'm wrong here please correct me.
 
I can literally post 20 articles that say PAO and Esters out perform group 3, machinelube has many of these articles with science behind them. So what? What do we do, convince people of something that we think we believe in? Ignore when a group a guys come here and say we are getting this result because we believe group 3 is the greatest stuff since sliced bread and we can't believe in anything else despite most of the evidence says this is wrong? The next greatest specs starting gf-6b Oronite is telling you cannot be met with group 3, they will HAVE to be other base oils, they have squeezed every ounce they can from HC, so they are just wrong? I urge people who have applications that may not be being served well with HC to do their own research. Many many engines out there are having issues with gf-5 and low viscosity, everything from cam lob wear to engine bearings. The answer very well may be pao/ester and/or going up in viscosity, and the only downside is costs a lil more for an oil change. People live in the cold, pao is the way to go, people that have engine hot spots like conditions like ticking, esters are the way to go.
 
Ever notice that they never have any of these charts that show group 3 can take down any base oil? Notice how in all of these charts that find themselves in the white papers always show the extra benefit of different base oils?

[Linked Image]
 
I thought additive was more important than base? In my older cars HC grp3 ran great and I was content. PAO bases are better but not all oils use them. Staying with Redline Oil minus one quart to slightly lower the cost and other variables. Air and oil filtration are a huge part too. Good fuel and non severe usage a consideration too. Unless its super cold the grp3 is okay. Get super hot and its grp5.PAO has only a couple of flaws;lacks almost any polarity and isnt great in high mileage negligence motors.
 
20 year old data? Guess you have plenty of time to think of topics to post seating in LA traffic.
 
Originally Posted by PimTac
The way I understand it PAO is a general term. There are a number of different PAO formulations and most PAO based oils are a blend of those formulations. Same with esters.

So this becomes more complicated than the study above. If I'm wrong here please correct me.


PAO is a type of synthesized base oil. It's quite specific, not general. However, there are a few different grades (EG: SpectraSyn vs SpectraSyn Plus) with which there may be differences in VI and volatility, but this is the case with any category of base and the range may in fact be more narrow for PAO as the list of producers is reasonably short. The PAO family benefits from having a reasonably wide cross section of viscosities available as well, which isn't the case with Group III.
 
burla et al.:

The paper doesn't claim that Group I, II, or III are better base oils than PAO (Group IV). In fact, they state that PAO is the best as far as the resistance to oxidation (longer OCI) is concerned.

The point of the paper is that even the best base oil such as PAO will oxidize very quickly unless matching antioxidants in sufficient amounts are used. In other words, the additive package is crucial.

A few of the finished PAO-based oils did poorly in the oxidation tests because their antioxidants didn't do the job. So, these oils would result in short OCIs.

If you have a PAO base oil and a good antioxidant, it will certainly do very well in oxidation tests and have a long OCI.
 
Originally Posted by burla
I can literally post 20 articles that say PAO and Esters out perform group 3, machinelube has many of these articles with science behind them. So what? What do we do, convince people of something that we think we believe in? Ignore when a group a guys come here and say we are getting this result because we believe group 3 is the greatest stuff since sliced bread and we can't believe in anything else despite most of the evidence says this is wrong? The next greatest specs starting gf-6b Oronite is telling you cannot be met with group 3, they will HAVE to be other base oils, they have squeezed every ounce they can from HC, so they are just wrong? I urge people who have applications that may not be being served well with HC to do their own research. Many many engines out there are having issues with gf-5 and low viscosity, everything from cam lob wear to engine bearings. The answer very well may be pao/ester and/or going up in viscosity, and the only downside is costs a lil more for an oil change. People live in the cold, pao is the way to go, people that have engine hot spots like conditions like ticking, esters are the way to go.



Really? You just posted fluff and marketing. Add hyperbole about wear you show your lack of knowledge and comprehension. Base oil is a start to meet a goal there is no catch all. You posted non sense because PAO and Esters alone make poor oils both need serious balanced additive packages and careful blending to make a finished product and are far from miracle fluids.
 
And to further dave's point, PAOs and esters (as well as HC oils) used in things like gearbox lubes, compressor sumps, etc... do not have to deal with combustion byproducts. It's one of the main sources for contamination, chemical breakdown, and acid formation which is what generally results in having to change engine oil.

burla, has Redline's check cleared yet this pay period?
 
Originally Posted by SubieRubyRoo
And to further dave's point, PAOs and esters (as well as HC oils) used in things like gearbox lubes, compressor sumps, etc... do not have to deal with combustion byproducts. It's one of the main sources for contamination, chemical breakdown, and acid formation which is what generally results in having to change engine oil.

burla, has Redline's check cleared yet this pay period?





I think he has been down ever since it was found out that Redline is rebottled Kendall.
 
Originally Posted by burla
I can literally post 20 articles that say PAO and Esters out perform group 3, machinelube has many of these articles with science behind them. So what? What do we do, convince people of something that we think we believe in? Ignore when a group a guys come here and say we are getting this result because we believe group 3 is the greatest stuff since sliced bread and we can't believe in anything else despite most of the evidence says this is wrong? The next greatest specs starting gf-6b Oronite is telling you cannot be met with group 3, they will HAVE to be other base oils, they have squeezed every ounce they can from HC, so they are just wrong? I urge people who have applications that may not be being served well with HC to do their own research. Many many engines out there are having issues with gf-5 and low viscosity, everything from cam lob wear to engine bearings. The answer very well may be pao/ester and/or going up in viscosity, and the only downside is costs a lil more for an oil change. People live in the cold, pao is the way to go, people that have engine hot spots like conditions like ticking, esters are the way to go.


I like the thinn oils over the thick oils. Will see how faar i will get with them in my honda. Toyota is using 0w-20 in eu too with great resultat.
 
Originally Posted by Gokhan
burla et al.:

The paper doesn't claim that Group I, II, or III are better base oils than PAO (Group IV). In fact, they state that PAO is the best as far as the resistance to oxidation (longer OCI) is concerned.

The point of the paper is that even the best base oil such as PAO will oxidize very quickly unless matching antioxidants in sufficient amounts are used. In other words, the additive package is crucial.

A few of the finished PAO-based oils did poorly in the oxidation tests because their antioxidants didn't do the job. So, these oils would result in short OCIs.

If you have a PAO base oil and a good antioxidant, it will certainly do very well in oxidation tests and have a long OCI.


Thanks, good info.
 
Originally Posted by dave1251
Originally Posted by burla
I can literally post 20 articles that say PAO and Esters out perform group 3, machinelube has many of these articles with science behind them. So what? What do we do, convince people of something that we think we believe in? Ignore when a group a guys come here and say we are getting this result because we believe group 3 is the greatest stuff since sliced bread and we can't believe in anything else despite most of the evidence says this is wrong? The next greatest specs starting gf-6b Oronite is telling you cannot be met with group 3, they will HAVE to be other base oils, they have squeezed every ounce they can from HC, so they are just wrong? I urge people who have applications that may not be being served well with HC to do their own research. Many many engines out there are having issues with gf-5 and low viscosity, everything from cam lob wear to engine bearings. The answer very well may be pao/ester and/or going up in viscosity, and the only downside is costs a lil more for an oil change. People live in the cold, pao is the way to go, people that have engine hot spots like conditions like ticking, esters are the way to go.



Really? You just posted fluff and marketing. Add hyperbole about wear you show your lack of knowledge and comprehension. Base oil is a start to meet a goal there is no catch all. You posted non sense because PAO and Esters alone make poor oils both need serious balanced additive packages and careful blending to make a finished product and are far from miracle fluids.


No thanks, bad info.
 
Originally Posted by Gokhan
burla et al.:

The paper doesn't claim that Group I, II, or III are better base oils than PAO (Group IV). In fact, they state that PAO is the best as far as the resistance to oxidation (longer OCI) is concerned.

The point of the paper is that even the best base oil such as PAO will oxidize very quickly unless matching antioxidants in sufficient amounts are used. In other words, the additive package is crucial.

A few of the finished PAO-based oils did poorly in the oxidation tests because their antioxidants didn't do the job. So, these oils would result in short OCIs.

If you have a PAO base oil and a good antioxidant, it will certainly do very well in oxidation tests and have a long OCI.


And you have the same situation with "Bio-Based" synthetic oils.

In formulating finished oils, one has to match the additive package to the mix of base oil types.
 
Originally Posted by MolaKule
And you have the same situation with "Bio-Based" synthetic oils.

In formulating finished oils, one has to match the additive package to the mix of base oil types.


^^ Exactly. You can have a synthetic oil with a weak ad-pack but be PAO or GTL based and not perform as well as a Group III with a great ad-pack. It's the total formulation that makes it perform and it's carefully balanced. It's also why I don't like adding anything to engine oils. You can upset this balance thinking you are doing something good when in fact you are not.
 
Last edited:
Originally Posted by StevieC


^^ Exactly. You can have a synthetic oil with a weak ad-pack but be PAO or GTL based and not perform as well as a Group III with a great ad-pack. It's the total formulation that makes it perform and it's carefully balanced.




Back in the early days Bob would remind us of that quite often. I think there are a few people on here that obsess a bit too much over what the base oil is made of. Sure it's good info to know, but it's not the entire story of an oil's performance by any means, especially if you're not going to do extended intervals or start your engine at -40 degrees.
 
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