# Iso Vs Sae



## planeflyer21 (Mar 28, 2016)

I see lots of questions on here about "What oil do I use?" and lots of references to the preferred ISO oil types.

Found this page showing ISO types and their SAE equivalents: 
http://www.engineeringtoolbox.com/iso-grade-oil-d_1207.html


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## British Steel (Mar 28, 2016)

Thanks Jon - doesn't go down to ISO 5 though (my lathe's beverage of choice - and it keeps spilling it, I think it has a drinking problem)

Dave H. (the other one)


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## Garththomas (Mar 28, 2016)

Its interesting that Ive been reading a lot about people using 20wt oil instead of iso68 and didn't know why. duh I am a nube thanks for the post.


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## Bob Korves (Mar 28, 2016)

Note that the ISO index or SAE "weight" is just the viscosity of the oil, it says nothing about anything else.  Some additive packages are for gasoline IC engines, some for diesel, some for gearboxes, some for hypoid gear boxes, some for way oil, etc.  The same ISO index is not necessarily the same oil for the same application, most likely not unless you are careful.  All it tells you is how fast the oil flows through an orifice at a standard temperature, nothing else.


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## Tozguy (Mar 29, 2016)

Most IC engines require detergent in the oil to handle the byproducts of combustion. Detergent is not necessary for a lathe but not harmful either. To my mind, general purpose non-detergent oils in SAE viscosities are perfectly suitable for a lathe. The container might even mention the ISO equivalent.


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## mksj (Mar 29, 2016)

Tozguy said:


> Detergent is not necessary for a lathe but not harmful either.



Usually this is not recommended for machines that do not have pressure lubrication with a filter. The detergent lifts all the particles/moisture and suspends it in the oil where you do not want it, motor oils are designed for different heat ranges, have additive packages, waxes, etc. Any oil will work, it just a matter of how well it work over time under the operating conditions. At the core is getting the correct viscosity specified by the manufacturer and the ambient/operating temperature. Different oils have different additives packs for the particular application, all will lubricate. Since one changes the oil infrequently in machines, for the smaller geared machinery I would use a gear oil as opposed to motor oil , and one that is readily available. There are lots of testimonials about using motor oils in their lathe for 20... years and it worked fine, but motor oils are designed for IC motors. I would not advise using motor oils or limited slip gear oils for small machinery gearheads.

http://www.practicalmachinist.com/vb/general/why-non-detergent-oil-143533/
http://www.chaski.org/homemachinist/viewtopic.php?f=42&t=74083&start=15


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## Tozguy (Mar 31, 2016)

mksj said:


> Usually this is not recommended for machines that do not have pressure lubrication with a filter. The detergent lifts all the particles/moisture and suspends it in the oil where you do not want it, motor oils are designed for different heat ranges, have additive packages, waxes, etc. Any oil will work, it just a matter of how well it work over time under the operating conditions. At the core is getting the correct viscosity specified by the manufacturer and the ambient/operating temperature. Different oils have different additives packs for the particular application, all will lubricate. Since one changes the oil infrequently in machines, for the smaller geared machinery I would use a gear oil as opposed to motor oil , and one that is readily available. There are lots of testimonials about using motor oils in their lathe for 20... years and it worked fine, but motor oils are designed for IC motors. I would not advise using motor oils or limited slip gear oils for small machinery gearheads.
> 
> http://www.practicalmachinist.com/vb/general/why-non-detergent-oil-143533/
> http://www.chaski.org/homemachinist/viewtopic.php?f=42&t=74083&start=15



If you advise against using a detergent engine oil of the recommended viscosity in a lathe gearbox , is it because it will harm the lathe or because it is not your first choice?


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## mksj (Mar 31, 2016)

It is not recommended, there is no definitive answer. I have yet to have come across a lathe manufacture that recommends a detergent oil for a non-pressurized lubrication system system. Motor oils are designed to meet viscosity specifications at operating temperatures that are much higher than you would experience in a lathe, so the effective viscosity could be quite different at lower operating temperatures seen in a lathe. There are anecdotal reports of lathe gear heads getting much hotter with the use of motor oils, most likely this is a viscosity issue. As mentioned, all oils will lubricate, will you see the affect of using motor oil in your lathe in 10-20 years, probably not. That being said, in my gearhead lathe, I picked up about 100 RPM on the top end, the head runs much cooler and I have much less foaming running a high quality gear oil.   I guess I just don't follow why one would not use the manufactures recommendations on choosing a lubrication oil for a specific machine.


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## tq60 (Apr 1, 2016)

Detergent oils keep things in suspension so the filter gan remove it.

If no filter then it wears out the item.

Use "good" oil in your lawnmower and it does not last as long as the cheap non detergent stuff. ( non filtered ones)

The artifacts settle to the bottom of the pan.

A gear head lathe with just splash lube needs good flowing oil but non detergent type to insure things are not held in suspension to get where it can cause harm.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


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## Tozguy (Apr 1, 2016)

mksj said:


> It is not recommended, there is no definitive answer. I have yet to have come across a lathe manufacture that recommends a detergent oil for a non-pressurized lubrication system system. Motor oils are designed to meet viscosity specifications at operating temperatures that are much higher than you would experience in a lathe, so the effective viscosity could be quite different at lower operating temperatures seen in a lathe. There are anecdotal reports of lathe gear heads getting much hotter with the use of motor oils, most likely this is a viscosity issue. As mentioned, all oils will lubricate, will you see the affect of using motor oil in your lathe in 10-20 years, probably not. That being said, in my gearhead lathe, I picked up about 100 RPM on the top end, the head runs much cooler and I have much less foaming running a high quality gear oil.   I guess I just don't follow why one would not use the manufactures recommendations on choosing a lubrication oil for a specific machine.



There is no argument about the mental security of following reliable recommendations. I have not seen anyone recommend an IC engine oil as better for a geared lathe than a machine oil is, just that it can be substituted for it. Regarding the contention that detergent oil would keep grit and water in suspension and harm the lathe somehow, it is news to me that my lathe is producing particles and water. If it did I would want to know about it and fix it! I wish people would stop making things up.

What oil were you using before you gained 100 rpm, less foaming and cooler running? 

In my case, although my shop is stocked with various engine oils, I bought a pail of ISO32 anti-wear hydraulic oil for my lathe simply because it is less expensive than the engine oils I buy.


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## mksj (Apr 1, 2016)

Tozguy said:


> What oil were you using before you gained 100 rpm, less foaming and cooler running?


Chinese gear head mill with stock oil, I went to a synthetic gear head oil by Amsoil. The difference was significant.

Please show me one lathe or mill manufacture that states motor oil can be substituted for gear oil in their machine. Moisture and condensation is always an issue, especially in more humid climates. Many machines have a crankcase breather tube, so they are constantly pulsating air into the gear case.

When you drain the oil, you often find a lot of particulates in the oil and it can be quite dirty, so if you don't mind having all this stuff floating in the oil, then go for the detergent oil. There are plenty of testimonials about the use of motor oils in lathes mills, etc. both pro and con. The There is enough reports in other forums about the machine running hotter (due to increase frictional shear) with the motor oil, that I still think one should stick with the proper recommended oil, as opposed to saving a dollar or two here or there. The other factor, just like in motors, change you oil at the recommended intervals.

I still disagree on the use of motor oil in gearheads, because the motor oil viscosity is designed around the operating temperatures of motors, gear oils are designed around much lower operating temperatures (usually 40C). The viscosity difference can be very significant. Putting 10W motor oil in your lathe might be closer to putting ISO100 at the operating temperature in a lathe.  The difference in viscosity for a motor oil at the two operating temperatures is about 3X.  Per Amsoil blurb: "Because an internal combustion engine has an oil pump and lubricates the bearings with a hydrodynamic film, extreme-pressure additives such as those used in gear oils are not necessary."
http://www.amsoil.com/newsstand/auto-and-light-truck/articles/dont-forget-the-gear-oil/?zo=34396



Gearhead oil was black and full of metal particles after 1 year.


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## Steve Shannon (Apr 1, 2016)

The South Bend Lathe Company, in the booklet "How to Run a Shaper", very specifically says "Do not use automobile engine oil or any oil which may contain a detergent" in the oil reservoir.
Grit and water are both byproducts of internal combustion, which of course does not happen in a lathe, but a certain amount of fine metallic particles would not surprise me just from wear. If your lathe is subjected to heating and cooling cycles and your air has any humidity at all you could have condensation as well. If so,  they would remain suspended in a detergent oil, but not in a machine oil.
Amsoil has a page that briefly discusses the differences between engine oil and gear oil, which points out that gear oil and engine oil each have different additives and why.
http://www.amsoil.com/newsstand/auto-and-light-truck/articles/dont-forget-the-gear-oil/?zo=34396


 Steve Shannon, P.E.


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## Tozguy (Apr 1, 2016)

This is a quote from the Amsoil link mentionned above:
'Motor oil contains additives such as detergents and dispersants to combat byproduct chemicals from gasoline or diesel ignition.'
Where is a reliable claim that detergent oils hold metallic particles in suspension more than non detergent oils? As a matter of fact, several of my cars and motorcycles have had a magnetic drain plug too. Why?

If your machine has a condensation problem then what happens to the water if the oil doesn't disperse it? 

If your machine is producing metallic particles in the gear box and using non-detergent oils will solve the problem then you are home free.

I am not advocating using the any viscosity oil in any type of gearbox. If your oil needs changing for any reason then change it. If a manufacturer specifies against using detergent oil then don't use them.  

I think that Bob kept it simple in post No.4


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## Bob Korves (Apr 1, 2016)

My post #4 was a warning.  You do not want to use vegetable oil of the correct viscosity in your machines unless it is specified.  RTFM.  Use the recommended oil.  Why do we think we need to outguess the designers and builders of our machines?  I will not necessarily follow brand name recommendations, but will use the correct type and viscosity of oil specified in any machine I am servicing, and at the recommended intervals.  I have never had an oil problem, corrosion problem, or excessive wear problem.  Coincidenza?


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## mksj (Apr 2, 2016)

mksj said:


> Please show me one lathe or mill manufacture that states motor oil can be substituted for gear oil in their machine.


An apple is not an orange just because it is round.
If you read the Jet lathe manuals they specifically state do not use detergent oils.
If you read the Grizzly lathe manuals they specifically state do not use detergent oils, and direct communication states concern to seals when detergent oils are used.
If you read the Clausing lathe manuals they specifically state do not use detergent oils.
If you read the SB lathe manuals they specifically state do not use detergent oils.
These lathe manuals specify use of gear oils not motor oils
The viscosity index for ISO gear oils is based on 40C, SAE motor oils is based 100C
The friction modifiers, foaming properties and rust corrosion properties are very different
The Amsoil blub on gear oil specifically states their formulation and properties is very different then motor oil. The title is
*"Gear Oil and Motor Oil Are Not the Same"*


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