Paraffin and engine oils

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The more parrafinic in nature the more stable and resistant to oxidatition, but also as parrafinic purity increases the ability to act as a solvent decreases. PAO is the ultimate parrafin.
 
As far as I know, paraffine is just another word for "wax". It is found in mineral oil but not in PAO which is "pure" synthetic. There is a minute amount of it in group III motor oil, the amount of paraffin increases dramatically in the lower grades. It is the main source of most of the sludge problems especially in the older cars / oils.
 
ISo Paraffinic nature also increases visocisity index.

The more paraffinic a base oil is the less impurities.
 
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Myth: Paraffinic base oils can cause wax buildup and sludge.
Fact: Not true. All high quality petroleum motor oils are made from paraffinic base oils. In spite of its name, "paraffin" does not mean candle wax. The stability of paraffin molecules makes paraffinic base oils more resistant to the chemical changes that can take place in an engine than other types of base oils. That means less sludge, varnish and corrosive wear with a high quality paraffinic base motor oil.
 
A paraffin is just a common name for a saturated C-H chain (hydrocarbon chain). In chemistry they are known as an alkane. The term paraffinic base oil is derived from the term paraffin, meaning a saturated hydrocarbon based oil.

Almost all motor oils contain, or, are mostly paraffin's (alkanes), including Group I, II, III, IV and many oils in Group V. The exception in motor oils are the ones based on esters (Group V) and other oils which are not paraffins in Group V, but a motor oil using only ester base oils is rare.

Paraffin is sometimes confused with paraffin wax. A paraffin isn’t necessarily a wax. There are paraffin type compounds and then there are paraffin waxes. The shorter paraffins (alkanes) like methane (CH4) and ethane (C2H6) are gaseous at room temperature. As the hydrocarbon chain gets longer ~ 10C, the C-H chained molecules become liquid at room temperature (oils), and when you have a long straight chain with ~20C atoms or more, the molecules will form a crystalline structure at room temperature known as a wax.

PAO's are made from alkenes, which are not paraffins (alkane's). Alkenes = olefin = C-H molecule with at least one double C=C bond. Modern PAO's are hydrogenated to remove any remaining C=C double bonds (saturate the carbon atoms with hydrogen) to increase their thermal/oxidative stability, which in effect turns the chained alkenes in the PAO into alkanes, which are paraffin's. So, hydrogenated PAO's (Group IV) are paraffin's too.
 
In my previous post I said paraffin means wax, I never said candle wax.
Your first post also said PAO was the ultimate paraffinic oil,completely wrong. Just the opposite is true, that's PAO greatest strength.
Only mineral based oils have paraffin in them. This is one of the impurities they are forever trying to remove. Group III based oils have the lowest paraffin content of mineral based oils , yet it is the most desireable.
I am attaching this quick link to show you paraffin is removed from mineral oil and is not desirable.

http://www.texlube.com/oilmyths.htm
 
Please read Drivebelts post. He did an excellent job explaining.
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You are correct in your definition of paraffins. However, the real point I was trying to make is that the paraffins in mineral oil vs Pao have nothing in common. One is desirable one is not.
Sort of like tomatoes and pineapples. They are both fruit but no one will ever confuse the two. Anyway, Thanks for the link.
 
PAO and GTL lubes are synthesized paraffinic. base oils, Conventional oils are refined parrafinic base oils. They are all desirable as they are the chemical structure that makes the base oil. Witout paraffin you would not have a base oil. Paraffinic base oils have a non polar quality that makes it difficult for them to dissolve additives. That is why a pure PAO base oils and most group III's must be cut with additives such as AN's or esters and sometimes Grp 1 oils to carry the additive pack. The only difference structurally between the oils is the consistency of the molecules and the amount of aromatic impurities contained. A grp 1 has a lot of molecular inconsistency thus the lower viscosity index and the lower flash points. Grp II is much lower in impurities and more consistent thus its color is nearly clear with an amber tinge and it has a higher flash point and higher VI Grp III has an even Higher purity is water white and has a high VI and low flash point PAO reached this quality long before GRP III because the synthesizing process to create PAO was commercialized long before the severe hydro treating was. They both end up being close to the same product with PAO having an edge in consistency and purity because it is formed from a a pure olefin stream and not refined from mineral stock. The differences for most applications between grp III and PAO are narrow.

CH2 is a consistent among PAOs and conventional base oils. The undesirable aromatic hydrocarbons(Napthanics) are excluded or refined out to improve VI and resistance to oxidation.


Here is a link and sample of a journal that refers to this.
http://www3.interscience.wiley.com/journal/112468648/abstract
"Abstract
This study was conducted to determine the effect of hydrocracked base stock chemical composition on lubricant properties, oxidation performance, and antioxidant additive response. Fifteen hydrocracked base stocks and polyalphaolefins were analysed by mass spectrometry for paraffinics, and single-, double-, and multi-ring naphthenics. Low levels of aromatics were confirmed in all the base oils. A linear relationship was found between certain naphthenic structures in the base stocks and properties, such as viscosity index, aniline point, and volatility. Additivated versions of the base stocks were also screened in the rotary bomb oxidation test (ASTM D 2272) and the thin-film oxygen uptake test (ASTM D 4742). A relationship between the types of naphthenic structures in the additivated base stocks and oxidative stability was found. Base oils containing low levels of condensed multi-ring naphthenic structures exhibited superior oxidation performance, lower volatility, and poorer solvency. Furthermore, antioxidant structure had a profound effect on oxidative stability as the level of multi-ring naphthenic structures in the base oils decreased. These results suggest that deeper knowledge of chemical composition could help in selecting base stocks and additives to meet future product specifications."
 
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Originally Posted By: pev223
Your first post also said PAO was the ultimate paraffinic oil,completely wrong. Just the opposite is true, that's PAO greatest strength. Only mineral based oils have paraffin in them. This is one of the impurities they are forever trying to remove.


You are correct in a way
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-- as they do want to remove certain paraffins from oil, just not all paraffins. There are 3 general types of paraffins …

1) linear paraffins -- straight chain hydrocarbons or normal paraffins
2) iso-paraffins -- branched chain paraffins
3) cyclo-paraffins -- hydrocarbon chains with ring structures (naphthenes)

It turns out that you don't want the linear paraffins (1) in your base oil, so they are removed. The longer chain (C20+) linear paraffins can line up and crystallize too easily to form wax -- even at room temperature. So you either remove them by solvent dewaxing, or, you rearrange them by isomerization (isodewaxing = Chevrons name for technology) into more appropriate isoparaffins for use in your base oil. You keep the other paraffins (2,3) which make up your Group II/III base oils.

PAO's are hydrocarbon chains just as are Group II and III base oils are. It's just that PAO's have a different hydrocarbon structure compared to II/III. In other words, the C-H molecules in PAO are just chained together differently than for GII/III base oils. So a PAO is technically a paraffin (isoparaffin) too.

Interestingly enough, Group III+ base oils are made from paraffin wax and have an isoparaffin structure (branched chain structure) in many ways very similar to PAO's (that's why they have similar performance). Group III+ have a longer backbone with shorter varying length chains, whereas PAO's have a short backbone with longer C-H chains sticking out. It's the particular C-H chaining structure of PAO's that gives them a nice low pour point (they don't line up easily to crystallize). PAO can crystallize (form wax) -- they just do so at a very low temperature, much lower than the typical C-H chain in a Group II or even III base oils.

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The last two post are very interesting but have me confused on one point: are all hydrocarbon ring structures called naphthenes or only those based on benzene-type rings (aromatics)? I've learned a lot reading these.
 
Naphthenic structures are aromatics that can contain or be similar to benzene so your second assumption is correct. There are many members of this family. To increase purity these Ringed hydrocarbons are removed as they lower VI and flash point as well as increase oxidation. They are more solvent and polar than the other paraffins which explains why a grp 1 oil has more solvency than the higher grp numbers do.
The more of these ringed hydrocarbons are removed or converted through hydro processing into linear and iso paraffins the more pure a mineral oil becomes. An assembled synthetic such as PAO is built without these ring structures in the first place but the hydrocarbon chains in PAO and thus the performance can still be improved by further hydro processing.
 
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