View Full Version : Understanding oil types

07-31-2010, 10:26 PM
Would someone explain the different types of oil? I realize it gets wildly complicated if we expand to non-petroleum based products but even if we stick to those, it seems pretty complex. Google is little help. Between grease and light sewing machine oil....I understand different viscosity but don't get the other attributes. For example, how does automatic transmission fluid compare to 30 weight? Is ATF and oil but brake fluid is not? Can any oil be used as a hydraulic fluid? Is wd-40 an oil? What is a "cutting oil" used on a sharpening stone? Is that any lubricant that will carry away the fines? Only use water on a water stone (?) but anything goes on other types? So any petroleum oils "build" and harden on a surface like tung oil? Didn't I see someone recommending soaking varnish brushes in ATF? Seems odd since I go to a lot of trouble to clean the surface before putting the varnish on....or is it so light it evaporates?

I shudda become an engineer.


Many thanks


Lew Barrett
07-31-2010, 11:20 PM
Is this a trick question?

In the good old day oils were made from a broad range of other (not petroleum based) natural products; whales, fish, nose grease, what have you. In fact, the lubricating qualities of whale oils are so great and special that they were specified for use in space.

Be that as it may, modern chemistry is so marvelous (ain't it now?) that they can make a lobster dinner out of light sweet crude and the only way to tell the difference is when your liver and kidneys go kablooey. Ever eat "kana" in a Japanese restaurant? Ever wonder what they make it out of? I have done both! Eaten it and wondered! So.......most lubricants and greases (like 99.999%) are some petroleum compound or another. A good understanding of the various different requirements and properties of the fluids that run inside most modern machinery can begun to be garnered here:

Read This (http://en.wikipedia.org/wiki/Motor_oil)

I bet Clan Gordon could write a tome on the topic! Maybe he already has?

Bottom line: This is a big question to crack!

Lew Barrett
07-31-2010, 11:29 PM
Brake fluid is something of a special case product. Read about it here, bears on hydraulic fluids. (http://en.wikipedia.org/wiki/Brake_fluid)

Synthetic motor oil gets it's own topic heading here (http://en.wikipedia.org/wiki/Synthetic_oil).

Store varnish brushes in Diesel or kerosene if you are looking to use the traditionally called for fluids in that application.

08-01-2010, 02:27 AM
Rendered bear grease does not get rancid, can be used in a number of situations, whale oil I have, candles, machine oil etc for clocks/instruments (like my sextant).
Other oils of various viscosity are made by "cracking" the crude, using heat to separate it out, changing the volatility and lubricity of the product. Natural petroleum is cheaper by far than any of the other possible sources, and modern chemistry makes improved products possible.

08-01-2010, 07:46 PM
All modern automotive fluids are engineered to meet specific requirements, for example automatic transmission fluid will have anti foaming agents in it because there is a lot of stirring action in a transmission.

http://carbibles.com has some good explanations of engine oils (amongst other things).