I looked into it a few years ago when I got a diesel as my "survival vehicle". It really is just a niche market sort of thing, not a sustainable for-the-masses option, and the idea of SHTF food crops being diverted to make fuel for just tooling around like everything is cool is a no-go. Not quite in the same league as using $25 per gallon moonshine to run your motorcycle at a fraction of the efficiency of gasoline, but you get the picture.

It kind of works if you are in a country area on the edge of a major city where other people don't have the whole waste grease market all hogged up, then you sort of get your fuel for "free", kind of, except that you are running around a day or two a few time a month picking up jugs of the fry grease and then spending another day running it through the home refiner.

My conclusion at the time was I was better off just getting a couple 55 gallon drums of farm diesel, calling it my SHTF stash, and calling it a prepared plan.

One concept in favor of the Diesel is that if SHTF, the "powers that be" will most likely see Diesel as being of strategic importance and keep supplies flowing in some form, while supplies of high octane gasoline might not be around at all.

What I found out (the hard way) is that a lot of insular communities don't even want Diesel sold at their gas stations because they don't want truck traffic after hours, There are huge stretches of highway 101 (the main north/south coastal highway in the Western states) where you can't buy diesel at night at any price, and some of the little towns along the Oregon coast have arranged not to sell it. Had some smug fuckers explain that to me when I ran out of fuel, and was going town to town on my reserve trying to find a place to that sold it one night heading home after a gun show. The real thing to worry about along that stretch is people knowing you are loaded with guns and gear after a gun show and just following waiting for you to run out of fuel, and even if you have AAA, take bets on how much of that cool gear will still be in your truck by the next morning.

Now for keeping a farm or industrial site going, maybe it would be smart, but then so is just getting some big fuel tanks and filling up with farm diesel.

Theoretically they can fine you pretty heavily if they find the red diesel in your regular truck fuel tank but if WROL, that don't matter much. If you know how to remove/disguise the dye, then they will never figure it out anyway.