Confused about ester, ester based, synthetics, etc...

[Nano]

I keep reading about esters, synthetics and semi-synthetic,

for example

Motul claims to be 100% esters.. some vegetal ones too...
Mobil claims to be synthetic but then some people say it's semi synthetic.
Redline is another ester based(?) 100% synthetic
Castrol seems to be semi synthetic...
Royal purple is another synthetic...
Torco SR-5 is another ester (based?)

I honestly don't get it, do esters have anything to do with synthetic? Is there a difference between a synthetic, an ester based and an ester oil?

Thanks,

 

[AndyH]

quote:

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Originally posted by Nano:
Mobil claims to be synthetic but then some people say it's semi synthetic.

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Mobil 1 is a true synthetic, you must be thinking of their semi-synthetic Mobil 7500 oil.

quote:

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Originally posted by Nano:
Castrol seems to be semi synthetic.

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The "German" Castrol Syntec 0w-30 available at AutoZone stores is a true synthetic oil.

 

[labman]

Chemically an ester is the product of an acid and a hydroxyl. The 2 oxygens in the linkage attract electrons from the rest of the molecule, leaving it with a slight positive charge and the oxygens a negative charge. This causes viscosity to be less affected by temperature and helps clean polar contaminates out of the engine. Most of the esters used in oil use either multi functional acids or polyols. Combine both, and you can have polyesters.

Another technique is poly alpha olefins. They are chemically similar to good old dino, but their different shape also make the viscosity less subject to heat.

The semi synthetics or blends are just mixtures of one of the synthetics and dino.

Originally a simple distillation of crude provided as good of a lubricant as was available then. The stuff under ground for millions of years was already reacted with anything it could, and was very stable. Later, we developed ways of doctoring it up with additives to make a better lubricant. This reduced the stability. The big advantage of the synthetics is that they require less additives. The esters may have better inherent lubrication properties too.

Having spent 10 years of my life making paint resins out of polyesters and vegetable oils, I avoid mixing different esters and vegetable oils. Either can grow polymers in your engine.

 

[Ray H]

Esters bring at least two desirable qualities. They promote seal swelling, and have been used to counter seal shrinkage issues with PAO-type synthetic oils. Additionally, since esters are "polar" molecules (they have a "+" and a "-" end), they'll align themselves with the opposite polarity of and adhere to metal surfaces for startup protection. Certain esters are very good at promoting cleanup, too. Specific esters can be custom synthesized, but they're found abundantly in nature, too. ALL vegetable oils and animal fats are esters. Westward treking pioneers used beef and/or mutton tallow to lube their wagons' wheel bearings. At some point, some brainiac discovered by chance that finely ground molybdenum (found as rock-like outcroppings) felt "greasy". When added to tallow, the combination considerably extended the working life of the lube with less bearing wear to boot.