A friend of mine and I made thousands of litres of bio...1000L at a time.
He was an expert in it and did things people said couldn't be done and tried every way of doing it. I myself have always preferred blending, Mixing with ULP mainly, never diesel, it's illogical, and had good success.
Why Make Bio? A number of reasons.
Firstly, people are pedanitc and scared. They worry about blowing up their engines ( which are often old in crappy vehicles anyway) and want to minimize the risk. At the risk of causing offence ( harden up) Americans are the worst at this. Many are just over the top and so worried they create more problems than what they solve and VERY often invent problems which either don't exist at all or are Million to one shots. Others do to but in my almost 15 years in the veg game, some are much worse than others.
making bio makes people feel safe even though then then go to stupid lengths and make mountains out of molehills from there. They worry about soaps and residual meth etc hen in fact the engine don't care a shit.
Summary: Fear of using oil straight or blended.
2nd reason: Not all engines/ pumps are compatible.
Newer Pumps are pretty weak and many will survive Bio where they won't run oil. These are pretty much anything electronic. I have Considered cars like the Merc ML's later Nissan patrols and Vw's as replacements for my 4.2 GQ patrol. I have found lots of people running these on the net long term on bio, very few if any on oil/ blended. Again may be fear but I too would be fearful of running oil unless I could blend it with kero or jet fuel which I do not have a cheap/ free supply of.
Some older diesels are harder to start on oil/ blends and there is also this mentality that an engine must start as soon as you even think about turning the key. Many seem to think 5 seconds of cranking means the engine won't start. I don't care if it takes 5 sec, as long as it takes 5 sec every time. Nothing wrong in my book with winding an engine over a bit to get some oil pressure before the thing lights off.
Bio being thinner lights off a lot better in some engines. In my old Merc I could start on bio better than diesel often. Straight oil in anything but the heat of summer was a drama for the first start of the day.
My current vehicle will start on straight oil just fine down to about freezing. Takes a few sec to wind up but in anything bar mid winter it don't care a lot. The merc and the Peugeot I had would absolute need a shot of methanol ( which I got from my bio making friend) down the intake to get them going and it would be a rough, very slow start. A lot depends whether the engine is direct or indirect injection and the compression ratio.... or engine wear.
I have never blened by Viscosity, I think that is a myth basicaly. If you look at the viscosity tolerance for Mechanical pumps particularly the Bosch inlines and rotary pumps, they will handle fuel thick enough that you can get down the fuel line. One of the reasons all this preheating the fuel to thin it is also a misnomer and parroted load of crap. At worst all you need to do is get it above the fat melting point, 30oC or so and you are fine. If one is like me and pays attention to their filtering, you won't have fats in the oil down to way below the ambient temps at the time anyway. I used to run a small pre heater to keep the fats out of the filter but haven't for years since I have improved my filtering process. Now if I am going somewhere the temps may drop a lot, I simply add some hose around the radiator hose. Time the fats get thick enough on the filter to block it, there will be enough under bonnet heat and temp on the fuel to melt it anyway.
The best way to eliminate fats it to DRY the oil. This raised the gel point Hugely. Adding some ULP also helps keep the fats in soloution.
I started out with oil adding 20% Ulp which was way too much in the early summer I started and I wouldn't add that much in winter now. 15% is my limit because then you start having other problems with Cavitation and the fuel boiling and causing air locks when the engine is up to heat.
I have found 5% ULP in warm weather as a minimum will improve starting and running an make for best over all performance. I'm lazy and tight and don't add that much anymore. as the weather gets cooler the ULP can be upped. Go by the starting of the engine. I don't add more than 10% in my vehicle these days but as said, 15% would be my limit. If I couldn't get good starts then, I'd go to a 3 part blend of Kero or turps added in.
Bio has it's place.
You can run that in vehicles you'd kill on blended oil and you cannot get the viscosity down low enough with ULP before you get too much in the mix and cause other problems in cold enough weather.
making Bio where I am is a fraction of the price of buying Diesel. As far as the old crap of " Your time" goes, I don't work 24/7 so when I made it with my mate, it was a very profitable hobby that paid a far better rate than either of our day jobs.
If you can get away with using blended oil, great. Do that and don't worry about bio making.
If you have something later or oil fussy, Bio is much better way to go than pump diesel.
Many people also believe that bio is pour in and oil takes a lot of modification. The old saying used to go modify the fuel or modify the Vehicle.
