As fuel prices rise it becomes more important to find alternative fuels for our vehicles and equipment. I hope to soon be cutting my diesel with used motor oil. You don't want to just poor dirty motor oil into your tank unless you want to destroy your engine. You must remove the water and filter it first. I plan on doing this by heating the oil above 212 degrees Fahrenheit to evaporate the water out then running it through some filters. I will run it first through a coffee filter to get the large particles out and then through this filter.
Thanks to Tim Glance of Old Grouch Military Surplus for the tips and a response to email. He was interviewed on The Survival Podcast here.