Mineral oil offers lubrication, cleanliness and low pressure that you can't get with other types of oil such as diesel, adding motor oil to it run the risk of burning your shop down, so you should not risk all your investments just to save a few bucks on some cheaper oil.
Vet oil or the tractor supply oil has about 15 CST, they're thick oil. In 15 CST when the blade is dip into the cut, it has to go into the cut and then flow back out. The viscosity is doubled from 7 to 15 CST so what happens is it can't escape fast, and it generates friction because it's trying to escape and flush the cut.
New oils are being drag in so the result is it doesn't flush the cut well, the pressure on the blade goes up because it's not flushing well and the blade will get dull faster.
Why does using mineral oil with 7 CST better?
✔️ It cleans better especially when you use the Everclean in separating, it's faster and easier because it has lower viscosity.
✔️ It will keep the blade sharpen, but you still need to sharpen your blade on a regular basis especially if you're cutting a lot of hard petrified wood or Jaspers.
✔️ It has no additives, no petroleum distillates or other kinds of stuff.
The combination of a good mineral oil and proper maintenance on keeping the blade sharp, makes your feed components and blade pressure last longer.
If you use thicker oil there's a higher risk that the blade will pull the rock out of the saw and might lead you to buy another blade.