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Old 10-20-2008, 06:38 AM
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Quote:
Originally Posted by desertdriver View Post
Dont confuse yourself with the synthetic vs petroleum oil arguements. Its all about hydrocarbon chain length and its relation to temperature dependent viscosity. All synthetic oils are hydrocarbons, just like petroleum based oils, they just have different polydispersity(better in synthetics). Think like a scientist not a lawyer. Molecular physics is molecualr physics, whether you pull the molecules out of the ground or synthesize them in a lab or plant the behaviors are consistent. the greater polydispersity of the mineral oils make them a bit better at lower temps.


Here is an article that compares the two if you care to read it. The (petroleum based)mineral oils actually lubricate better at low temps(thicker film before parts expand). this means that its even more important for synthetics to warm them up. Yeah, I used to be a metallurgist, so I know about expanding metals.

http://www.machinerylubrication.com/...?articleid=586
1. Your statement that all synthetic oils are hydrocarbons is absolutely false. Many of the best synthetics are esters, diesters and polyesters, therefore they have oxygen atoms in the molecular chain, thus by definition they cannot be hydrocarbons.

2. The study you posted is about gear lubrication at high temps, not even a valid comparison to engine lubrication at low temps. Note the lowest temp tested was 50C or 122F. While I agree that there may be times that a mineral oil may be better than a synthetic the question is much more complex than that. There are many variables including the type of synthetic.

However, why don't you ask your engine if it is starting at 20 below zero if it would prefer a solid mineral oil frozen at the bottom of the crankcase performing no lubrication at all or a synthetic that is liquid and is actually being pumped throughout the engine and to the top of the cams. My friends that is where 80% of the wear on an engine takes place and where mineral oils fail severely compared to a good synthetic.
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