I am wondering if you use motor oil to quench if it all has to the same type or not. Can you use 0w-20 with 30w-40 as a example 

I would avoid motor oil all together. With the additives in modern motor oil, the fumes from quenching can be very hazardous. If you have the funds available, actual quenching oil is the best think to use and is formulated with different quenching speeds for different steels. The common alternative is canola oil warmed to about 120F (which reduces the viscosity and increases quench speed). 
What type of steel are you working with? That make a huge difference in what you use. Many medium carbon steels harden with water and some higher carbon steels are formulated to quench with water also…

Keep it fun,

David

Welcome from the Ozark Mountains. I agree with Goods and new motor oil is generally more expensive than say canola or peanut oils, which often be obtained for free. I suggest reading through the pinned thread about used motor oil.

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

Welcome aboard Jesus, glad to have you. If you put your general location in the header you'll have a better chance of meeting up with members living within visiting distance.

Yes, motor oil types, weights, etc. should be consistent. Consistently ABSENT! Other than some in an oil can to lubricate machinery in the shop motor oil has NO PLACE there. Like David says, even new clean motor oil has additives that that are health hazards some serious. Also it's generally a poor quenchant that requires thinning. What are you going to thin it with, ATF? Oooh, more BAD stuff.

Ahhh, I seem to be on a safety kick this morning I'll let it rest at that. 

Randy is right, deep fryer oil is WAY less expensive and is often available free if you don't mind your shop smelling like donuts or fried finger food when you harden something. 

Commercially made quenching oil like Parks will remain usable for hundreds of hardening cycles and does a better job because it doesn't degrade in use. 

This isn't the 1950s good quenchants are readily available, if you're going to go to all the work of making blades or whatever requires hardening why not finish it properly. You will know exactly what to expect using a commercially made product. Honest.

Frosty The Lucky.