As I have a variety of different suppliers, I "cold filter" all of the WVO, to ensure that my oil is liquid at the lowest ambient temperatures encountered in my location.
Since introducing "cold filtering" we have not had ANY fuel filter blockages due to tallow. My wife's "Josephine" does have a small heat exchanger in the fuel feed to the in-line prefilter, so that she does not get any surprises.

I have not tested the viscosity of my vegetable oil. It is a significantly thicker than diesel. The vegetable oil remains liquid at all operating temperatures we experience.

As I am not heating the vegetable oil before it arrives in the engine bay, flow thru the added OE fuel line is less than optimum, but as I have a "looped" return line, the flow thru the fuel line is much less too. I have a Holley Blue fuel pump on order and will plumb it in to overcome the fuel line pressure drop.
In my main fuel tank, I am running blends of 50:50 to 20:80% biodiesel:WVO, dependant on the season.

I do not have a prefilter in front of my electric fuel pump, but plan to install one before the Holley Blue, when I install it. This pump is a Vane Pump which has sprung loaded vanes, which are loacted in a cylinder offset from the centre of another cylinder, and due to the rotation, provides a positive displacement, pumping the fuel. It comes with an adjustable regulator, which I hope to locate after the fuel filter, so that the engine gets a constant fuel pressure.

I did research the MB fuel lift pump output pressure spec, on the online 300D (Turbo) manual. It was around 11-12 psi IIRC, but I measure 15psi at idle on mine. I haven't checked any other 300D's , but I presume that they will all be around that figure, as the spec was a minimum pressure, not a maximum pressure.

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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.