Two Letters Re: A Little Insight on Diesel Engines
I am prepper, survivalist, as well as a longtime waste vegetable oil (WVO ) user. I wasn’t gonna get in this diesel game, except that it saved my life. In 2004 I was in a severe commercial truck accident where I was struck in the fuel tank and rolled three times. When the EMT  was cleaning me up, she told me that using diesel fuel had saved my life. If I had been in a company truck that was gas-powered (Top Kick C6500) I would have died in a explosion upon impact. That was the day I became a diesel believer, and shortly later a grease diesel believer.
My family owns a 2000 Ford Excursion with a 7.3 Powerstroke, it is fully outfitted with bull bar, inverter, CB  radio, real front hubs, but most importantly a Vegistroke  (fully automatic WVO fuel system). I love this system and have 103,000 miles on it (including 60,000 miles on WVO) with original injectors. I have a range of 1,500-1,600 miles between diesel and WVO, which is perfect for G.O.O.D.  situations, as well as family vacations. We also own a 2005 Jeep CRD (diesel) that has a one-off kit with roughly 55K miles on WVO, original injectors as well.
My successful long term use of WVO was accomplished it part by doing it right: I have a centrifuge that cleans my oil to .5 (yes half a micron) absolute, as well as remove glycerin. It is a Dieselcraft OC-50 complete system, and the back bone to my way of life,allowing me to run my two SUV s and home for next to nothing. My home is heated with a AGsolutions b-150 boiler and gravity fed “Alaska” Bio-diesel stove (no electricity required), as well as a wood stove. We can generate enough electricity with my diesel generator (also runs on bio-diesel), to power the boiler, house and or make enough clean fuel to G.O.O.D., without an issue. We have lived this lifestyle for 5 years without a hitch, and intend on living this way no matter what political, economic, or SHTF  scenario comes down the road. – H.L., Prepared in New Hampshire (“Live Free or Die”)
In response to Rick B.’s stated apprehension about homebrewed diesel fuel: Yes all those cautionary concerns are true. Running any homebrewed fuel comes with consequences and extra maintenance issue. But I believe he is missing the point. There may very well come a day when you cannot afford to simply go to the pump and churn out clean dino-fuel due to unaffordable high prices or just plain old non availability.
So then what? Do you turn your prized diesel into a raised bed garden on wheels? No. You improvised adapt and overcome. You move on to the next best thing. And that is, knowing how to use your available resources to get moving.
I have used all kinds or reclaimed oils in several different diesels. I have used a mixture of 20% regular unleaded gas to 80% filtered veg-oil that I have reclaimed from restaurants. I have also filtered used motor oil (which also requires boiling to remove as much of the impurities as possible) mixed with #2 diesel to run my mechanical diesels.
I have used all of the above in my 2001 F-250 for years and have traveled several thousand miles at a time solely on processed oil and [a 20% mixture of] unleaded gas (not bio-diesel). Without any problems other than changing my fuel filter every 3,000 miles just to be cautious.
I have run the same mixtures in my 2005 Dodge 3500 with wonderful results. And my 1990 Ford 350 van loves it.
My point is, it can be done safely. Yes you do have to change filters more frequently. And yes you need to be extremely diligent about your filtering of any oil alternative before using it as fuel.
I do not mess with bio-diesel simply because the processes involved make it less post-TEOTWAWKI  friendly.
As for the internal combustion of these homebrewed fuels and the cleanliness of the engine, I can only speak for my self. My 1990 F-350 van was filthy internally, but after running veg-oil (not processed motor oil which can dirty up the engine ) for several years the engine was as clean as the day we rebuilt it.
So IMHO, when approached from the right mindset and through filtering, any waster veg-oil or motor oil is a very viable fuel source for any diesel not weighted down by excessive amount of electronic sensors (probably 2006 and newer).
But beware, do not widely advertise your fuel mixture. Because some states frown on using homebrewed fuel because they are missing out on you paying road fuel taxes. – A.S.W.
[JWR Adds: Readers are cautioned not to use gasoline blends in diesel engines, except in extremis.]