naphthenic vs. paraffinic lubricating oils

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I found this description from http://www.freepatentsonline.com/4515680.html

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Historically, naphthenic lubricating oils have been the lubricating oils of choice on a cost/performance basis. This has been particularly the case in formulating highly viscous oils used in heavy duty applications such as railroad and marine diesel engines. It has been the experience in the art that the naphthenic lubricating oils have the capability of dissolving and/or softening significant quantities of the semi-solid carbonacous decomposition products which form in crank cases under severe operating conditions. The semi-solid carbonacous components formed on the cylinder walls and suspended in naphthenic lubricating oil in the crank cases of diesel engines tend to be softer than the corresponding carbonacous products formed in paraffinic lubrication oils under identical operating conditions. By reason of their softer nature, the deposites formed from naphthenic lubricating oils cause less wear on moving engine parts. It is the belief in the art that diesel engines have a longer operating life when lubricated with naphthenic lubricants than is the case with paraffinic lubricants. Specifically, it is believed that the incidence of piston ring breakage is lower when naphthenic lubricating oils are employed.

By a quirk of nature, naturally occurring crude oil containing significant fractions of naphthenic hydrocarbons in the lubricating oil range are found largely within the continental United States and Venezuela. Crude oils produced in other oil producing areas of the world have relatively lower concentrations of such naphthenic hydrocarbons. Accordingly, as the worldwide demand for naphthenic lubricating oils is increasing, the available supply of crude oils containing significant concentrations of the desired naphthenic hydrocarbons is decreasing. It is thus seen that a shortage of naphthenic lubricating oils is developing.


Do we assume that PCMO is based on paraffinic lubricating oils and HDMO/diesel oil is based on naphthenic lubricating oils?

Thanks!
 
Paraffinics are used in all motor oils because they are much more resistant to oxidation. The sump on nearly all cars/trucks is fairly small, so oxidation resistance is critical.

The sump on a train is something like 200 gallons (anyone with a hard number please post) so oxidation is much less of a concern.

ETA:
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The new AC6000s have 5,500 gallon tanks. In addition to fuel, the locomotive will carry around, typically about 300 US gallons of cooling water and 250 gallons of lubricating oil for the diesel engine.

http://www.railway-technical.com/diesel.shtml
 
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Seems the locomotive engines and ship engines have different oil requirements than a high speed gas or diesel engine. That is why I post comment about reading an article and not knowing what we are reading about.
 
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