Best Saw Oil

I use stellar lubricants, a lapidary oil.
"Mineral oil" is often confused as something other than petroleum, but it comes from the same separating and refining process that gives us thick tarlike gear oils and extremely thin kerosene or gasoline. Mineral oil is merely a trade name, no minerals involved in it's production, just a highly refined oil. At the same viscosity, tech grade (veterinary and cosmetics), food grade, and medical grade are identical. The grading and cost differences are due to the testing and certifications and their cost.

Almost everyone I know cannot stand the scent of Stellars orange cutting oil, in my opinion it is worse then automotive hydraulic fluids.  The same guy that sells the Stellar also sells Bear Naked cutting oil, this is what I will typically buy when he or his vendors are selling at Q or Tucson. No scent and cuts well.  The Hplapidary cutting oil is getting good reviews as well, I have not tried it yet.

AzRockGeek Thank you! That is good to know! I can imagine it being a problem smelling up the garage even. I see his other Bear Naked product now.

The basic differences are in viscosity and from a practical standpoint, thinner means the solids (read rock dust) settle to the bottom of your tank and the oil floats on top and stays clear longer. Cleaning means scraping the detritus out like semi-dried paint from your old latex bucket. Thicker (read human laxative and to a lesser extent horse laxatives) will mean that rock detritus will remain suspended in the coolant (same clean out interval probably but in my experience easier in that its is removed like pudding. In my eyes they both have the same lubricating and cooling properties; but I suspect that the thinner stuff will mist more and hence contribute to the film of adjacent equipment and persistent odors. While some folks recommend baby oil and other things with fragrances, I am totally turned off by such intrusions in my shop. There is not best lapidary oil, except one that is readily available to you, within your cost range, and not as obnoxiously offensive as kerosene, diesel fuel, hydraulic fluid, or oils from electrical transformers that have toxic stuff unmentionable. Go home with the oil that brung you and don't fret too much about whether it was the best.

I have been using the "Horse Laxative" Mineral Oil for over 3 years and so far none of my 3 saws have had any problem with constipation!!

Does not seem to have any noticeable odor, and the only issue is the maintenance department is somewhat lax(no pun intended) with their cleanout schedule. With everything else being equal, the cost of the oil with free shipping of orders over $75, and the next day delivery to me is a big plus. With 3 saws a 24", a 20" and a 10" larger orders are my norm.

I do re-use filtered oil. My current filtering system is very slow and working on next upgrade using pillowcases or a suitable cloth sack and some adjustments to speed up the process. I have 6 gallons of filtered oil ready to use. If I can speed up the filtering process my orders should be less frequent.

There is a range you can use for sure, and with some research a person might be able to use zahn cups and make their own blend for each saw, but there are already not enough hours in a day. With larger blades I notice more mist if I open it immediately, so using the filtered oil, which is a little thicker, can help with that. I never add the thickeners like some do to control mist, most contain zinc and other nasty unhealthy chemicals. The only condition we're dealing with is where the blade contacts what it's cutting, we're looking for cooling, lubricating, and flushing debris away from the cut, pretty universal with all saws.
We're looking at CsT@40c viscosity 7-12 ideally, make sure it's @40c and not @100c. ISO numbers are pretty much the same, but have +/-10 tolerance so batches can vary wildly and the oils it's used for are generally stinky gear oils anyway. If it is measured in SAE it's too thick, 0-5SAE is 22 CsT.
Here in AZ in the summer I stop cutting generally at about 105 degrees f or allow a LONG cool down between cuts, the oil and blade have gotten hot enough that the blade gets wonky from heat expansion, thankfully it returned to normal when it cooled but the cuts with the untensioned hot blade are not nice smooth cuts.

I'll have to ask Kevin about the bare naked at Q and maybe switch to it when his last 55g delivery runs out.
I started with him buying oil for the club shop. When I joined and helped a member re-establish the club lapidary in a new location they were getting transformer oil from a member who got it by the drum. A couple well intentioned members began using the hydraulic oil when the other oil supply dried up, and I bailed for awhile because it was awful stuff. When members with reactions to it complained we found the stellar oil, everyone was happy with it. Their current new location has great ventilation for the saw area so that helps, but still no complaints to my knowledge. I was in my attached garage up north and never heard comments on the smell their either. I still separate oily, wet and dry operations, but not due to smell.

RFI:  Anyone ever plop a temperature sensor in the oil tank and plot the rise over the course of a cutting session?

Also curious, in the bigger saws, if any oil actually circulates top to bottom while cutting.

Food grade mineral oil. Almost water thin (even at 15 degrees the coldest I have run the saw at). Zero smell. Used to be cheap (on Amazon) but price has more than doubled. I filter it on clean outs and have not had to replace it yet (4 clean outs and counting).