What is the additive to convert cooking oil to diesel?

I have a mive ford F250 super-duty it runs on diesel and with fuel prices so high I might have to get rid of it. However, I heard about an additive for cooking oil that allows it to be used for diesel engines. I would like to know the name of this additive, the prices, where I can get it, and if it works. I know about the 2 tank converter kit and I don't really want to install that. I you know anything about this additive I would greatly appreciate your input.