Oil viscosity

OK I have searched for days about machinery oil and the question I have I would think it would be simple... However it seems that is not the case. I would love for this to be settled once and for all. I understand the difference between iso and sae ratings. I know about the Mobil oils. So without further ado here is the question/ statement... I own OLD equipment and whenever you see an oil to use they don't mention iso or sae, they simply state #10 oil or #30 oil etc. Now is that an iso rating or sae? Is "#10" oil velocite 6? I can't believe this answer is nowhere to be found. (I may not be searching properly) Please good people answer this question once and for all. When it says #30 oil what rating are they using? We are talking equipment from the 30s to 50s. From atlas lathes to delta scroll saws etc. Please someone end my misery and give me an answer. Thank you all for your great info. If anyone knows it will be on this site. To beat a dead horse, why do the old manuals just say #10, my only thought is that it was common and there were only 5 viscosities back then and it was simple. HA! Thank you again.

I have a 1941 south bend 10L and a 1947 9A.

The 9A has a oiling chart that states viscosity in SSU (seconds, Saybolt Universal) an the 10L specifies sae 20 for most if not everything....

I would ass ume the #20 or whatever would translate to the sae viscosity. However you need to consider what it is you are oiling. If it's gears it should be thicker, if it's a high speed bearing it should be thinner, if it's a way surface it should be tacky. Also understand that oils and lubricants have come a long way and modern oils have a lot better additives and engineering and process controls now. Basically if the oil is thin enough to get into the bearing and thick enough to maintain a film it will (gulp) probably be okay considering the recommended oils were more or less straight mineral oils with little or no additives.

Motor oil is not the same as lubricating/machine oil (hydraulic oil is really close) also bar an chain oil is not a good way oil.

Straight weight, non detergent mineral based oils.

This type of oil would hold the contaminates and they would fling to the outer parts and hold it there. From a time when most cars didn't have oil filters and ran similar oil.

All literature and info from old guys, is that most bearings were designed for straight 20 and most gearboxes for 30.

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There are many viscosity scales. You mentioned only two. SB used the Saybolt scale. It is close to the ISO scale. In this respect, Google is your friend. ISO 150 is close to a SAE 10 weight. ISO 350 is close to SAE 30 weight. Never use any automotive oil as machine oil. Automotive oils contain disbursants that keep contaminates in suspension for the oil filter to remove. Machine oils allow contaminates to settle into the sump. There is a lot to this subject, much more than what can be contained in this thread. Plus, there is the BS factor where you have responders here on this forum that are misinformed. Do your own homework.

Jack, Sir
Here's a chart from a nice company that may be of interest to you.
Resource Library
Just an observation about old machines and oil.. The mobil vactra and named circulating oils seem to cover most needs. Veloclite # 10 cover most older bronze bearing ( read plain ) needs.
Hope this helps
Stay safe
Calvin B

Where in Pa are you located ?

Here is a chart that I shamelessly stole from the internet that has been helpful for me.

Near the new York border around corning new York. Well comparison charts and the answers provided do not help if no one knows what they mean when they say " use #10 oil." I thought someone must have figured this out by know... So I am going to call Mobil tomorrow and then post the answer that I get. When it is stated in the old manual they say it like everyone knows, at least back then, so someone at Mobil should know what they were referring to. At that point It should be easy to figure out what the new and improved oils of today that should be used in its stead. I just can't believe that this question is so difficult to answer.

A for instance (and tell Mobil you want the latest edition of Brief Product Descriptions) is that both Mobil 10W30 and Mobil DTE Heavy Medium are both 335 SUS at 100 F, but one is for ENGINES and the other for MACHINE TOOLS

johnoder said:

A for instance (and tell Mobil you want the latest edition of Brief Product Descriptions) is that both Mobil 10W30 and Mobil DTE Heavy Medium are both 335 SUS at 100 F, but one is for ENGINES and the other for MACHINE TOOLS

Click to expand...

The Mobil DTE lacks detergent. Engine oil has detergent.

UTTO works for every machine tool gearbox application. It works for all Hydraulic applications that might be found in a machine shop, And it works for low speed oil lubed spindles.

I have standardized on the stuff! UTTO * Ask for it by name!

* Universal Tractor Transmission Oil.

Another reason to never use auto engine oil is that it is hydrophilic. It is designed to absorb moisure internally in the engine when it is sitting and then expel it thru the crankcase ventilation when the car is running.

The modern heavy gear oils, like rear-end lube, can be bad for yellow metal. It has to do with the high pressure additives after gl4. So gl5 or newer can have issues with bushings etc.
Bill D

Jack, Sir
To be blunt you don't know what you are asking for as your question only has half of what is needed to give you an answer. You need to know what scale the manufacture used to come up with #10, #30, etc.
AND as for folks having "figured it out"... Well Alot of folks have and they have posted the info here ( alibi some cryptically myself included, sorry bout that) So I'll spell it out for you in Mobil oil terms.
DTE medium = iso 46 or 20wt or #20
DTE heavy medium = iso 68 or 30wt or #30
velocite #10 is your go to spindle oil
vactra #2 is roughly equal to iso 68 or 30wt or 'good grade of way oil'
Much research on my part has went into that simple list.. Just saying.
As fur the internet "experts" that suggest tractor oil and synthetic motor oils... Well I've had my hands in many machines that were damaged by such internet 'wisdom' ( I have a nice southbend 16 that still has friction clutch issues two years after multiple flushes after some 'expert' put a 'super lube' in the apron)... So anyone who would show up my shop and try and peddle that stuff would get promptly punted over the hill.
Old machines like what they were made to run with and the modern made oils that are DESIGNED for them are almost the elixir of life for the old beasts..
Stick with a 'circulating oil' or a 'non-detergent' oil. If in doubt as to an oil.. take a small amount and put it in a glass jar with an equal amount of water and shake it up. Detergent oils will hold the water in suspension for ever.. most non-detergent oils and all circulating oils will separate out in minutes.. That's what you want.. A oil that will separate out water and let dirt settle to the bottom of the sump. Your machines will thank you.
Hope this helps
Stay safe
Calvin B

hm, now its getting complicated. what does "wt" actually mean? is it supposed to be the sae number (@100°c)? last time i saw it was when i filled up the shock on a rc-car.

if thats the case, then dte68, dte48 (lowest limit)and vactra no.2 wouild all be sae20.

Mobil oil company has some resources on there website. Industrial lubricants by equipment builder | Mobil™

They have their recommended oils for south bend lathes they may have recommendations for your equipment. The bottom line is you will probably have to use your own judgment. If the bearing clearance is small say less than .002 you will need a "light" oil, its better to have a lighter oil that can get in the bearing than one that's too thick.

Hydraulic oils are very similar to circulating oils they start out as the came base oils. A lot older equipment uses a total loss lubrication system. IMO if the bearing is oiled by total loss it doesn't matter much if the oil is the "perfect" oil it just has to get in the bearing. Spindle bearings need a light oil because the clearances are small the same is true for the wet feed clutch in a south bend, it wasn't damaged because hydraulic oil was used it was damaged because the oil was too thick to get in the space it needed too.

Don't make things harder than they have to be.