Tom,
I did buy the bio diesel, didnt made it myself. It was just a test how it does work. It was real 100% bio diesel, made chemically from cold compressed rape seed oil. It works lots of better than cold compressed vegetable oil without further treatments. Actually it works fine down to -17 degrees but no further. If you made it from palm oil it works fine down to -15 or something. Only cold compressed "raw vegetable" oil woks with heaters and dual
fuel system (at starting you use mineral based diesel and when engine is warm you change to vegetable oil) down to -5 degrees.
It is true that tractors like old mf:s or Zts with fuel tank on engine you can easily use vegetable oil in cold weather,but it means you must drive 16 hour a day then. I use my MF 165 for feeding cows everyday and each time takes about 15 minutes, so it wont get warm at all.... And its getting cold starts every day.....
At the moment its engine is so worn out it hardly can keep its oil preussure at summer, and it hardly can run at 1000 revs at winters. I think one winter more and i must send it to tractors cemetery
BTW, in some german calculations were studied about using vegetable oils (produced at fields) for traffic. The result was that technical problems can be solved, but........ If peoples want eat too in future, oil plants can be produced only at very little part of totally field area. It means in practice that only farming tractors can be used with rape seed oil, otherwice there is no enough field for food producting
But at the moment, (we get 110 euros/1000kg of barley (it is high at the moment) and farming diesel is 0.6640 eur/litre (it is low at the moment)), it is economically reasonable to grow rape and compress oil for heating purposes. Here heating oil is allways needed, and we need lots of oil every year for drying grain, because humidity when grain is harvested can be even 25 % sometimes.