Understanding oil specifications.
This is a good question and the first place to start when looking for good oil.
Some oil makers do not publish or supply all the specs. These ones I am always leery of.
I look for the basic four.
Flashpoint: Often ignored. Flash is a good indication of good base oil stock. No modern day oil that I know of is under 400 F and this is a minimum number. The higher the flash the better. If an oil specs out at 400 F or slightly above, warning bells should sound. Good dino oils and synthetics are over 450 F. Synthetics often spec out over 500 F.
HTHS: Each viscosity range of oil has to meet a minimum hths requirement. 15/40 for instance would have to be 3.7 minimum. Look for oils with high hths. Over 4.0 is good depending on viscosity.
Viscosity Index: Higher the better. 140 should be considered minimum.
TBN: Higher the better. 10 or more is very good.