Journey to Forever, A Japanese based environmental group recommends an SVO system and gives the following details. These are all European based companies which seem to be difficult to acquire in the US, but appear to be very sophisticated and built by well established companies:

"Single-tank SVO systems

With professional single-tank SVO systems there is no waiting or switching fuels as with two-tank SVO kits -- start up and go, stop and switch off, just like any other car. The engine starts easily and burns cleanly from the start, even at sub-zero temperatures. (Supplementary heating is available for really cold conditions.)

Single-tank SVO systems are suitable for both Indirect Injection (IDI) and Direct Injection (DI, TDI, PDI) diesel engines.

The "secret" is specially made injector nozzles, increased injection pressure and stronger glow-plugs, in addition to fuel pre-heating.

Journey to Forever uses a single-tank SVO system. They're the only SVO kits we recommend.

They are made by three companies, all in Germany. They are:

Elsbett Technologie, who have more than 30 years at the forefront of using vegetable oil fuel in diesel engines.

VWP, Vereinigte Werkstätten für Pflanzenöltechnologie ("combined workshops for vegetable oil technology"), founded about 12 years ago by former Elsbett employees.

WOLF Pflanzenöltechnik (WOLF vegetable oil technology) have been providing advanced single-tank SVO systems since the mid-90s.