I have been using WVO in my Mazda Capella for 3 years, using mainly heavily used Canola oil from a Fish & Chip shop.
I prefilter to 5 micron and plan to use an electric lift pump for the WVO, to ensure that sufficient veg-oil arrives at the IP.

The heated fuel filter was to ensure that any solidified oil is melted to allow the hot oil to flow. I suppose that a coolant, or electrical, heater between the WVO filter and the solenoid valve would be another option.

The return line solenoid valve is an interesting problem, with the Injectors, IP and filter returns connected together at the Filter.

I plan to maintain the existing return to diesel tank from the Fuel filter, and switch the Injector and IP returns to the appropriate fuel tank return line.

I know of 2 MB 300TD's running on tallow (beef fat), but they use only a clear plastic fuel filter and the fat in that seems to melt quickly once the engine warms up. He had the engine overhauled last year and the mechanic reported lower than normal carbon presence in the combustion chambers.
I have had some polymerisation fo the canola oil in the past, causing filter clogging, co it may be best for me to use tallow in preference.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.