oils as a top dress to feed(Deep fryer oil)

I have read somewhere that some people use like vegetable oil or oil from deep fryers as a top dress for more coverage.  Is there anyone that uses this? if so how much do you use.  I have a place that would give the deep fryer oil every month which would be equivelant to about 8 gallons of oil.  Would this be worth getting and top dressing with or would it be just a waste of time.  Is there anything that I should look for or ingredients that shouldn't be used in the oil?  I am just learning about all of this that is why I am posting and asking questions about the possibility of extra fats.

Thanks for all the help ahead of time.

I have used this quite extensively in the past. More for dust reduction than anything else. Dumped the stuff directly into the top of grinder-mixer while making homemade feed. It gets really hard to handle when cold, and turns rancid when kept warm. I'm not sure if it's worth the time and labor. You sure couldn't afford to buy the stuff!

And it is a case where less-is-more, you can use too much of the stuff.

I have used corn oil only. I has done wonders for us. With the new rules and regs regarding food animals consuming animal proteins, I would be hesitant to use something that might have had other animal proteins in it or cooked in it. I personally wouldn't use it and corn oil isn't that expensive when bought in bulk.