There are so many different types of asphalt sealers made with all different ingredients. The stuff I just put down on my driveway has ink, slate, clay, water, asphalt emulsion, and some other "proprietary" ingredients in it.
The stuff I use at work has a coal tar base for better oil/fuel resistance. We are now also looking into recycled rubber based sealcoat.
I don't think you will have much luck with used oil as petroleum breaks down and weakens asphalt
Generally, you can purchase sealcoats for $2-$2.50 per gallon and then add 10-15% water to the mix to thin it out and make it workable. Coverage depends on density of pavement...20 sq. ft./gallon for really boney stuff to 40 sq. ft./gallon for a tight mix. You can also add up to 2 lbs of sand per gallon to fill in some of the voids