From what I have read the issues seem to be two things; one, that manufacturers design in a cooling effect from diesel fuel for the injectors and/or IP to help cool them. Two, the effective firing of the fuels at too hot/cool temps.

There for I have wondered the same as you. Lately though, from what I have read, is that WVO helps pull heat out of the IP/Injector areas better than diesel there for a hotter solution of a WVO mix will cool as effectively as normal temp diesel fuel. Now with that said.... if your running a two tank system you can allways turn things off. Put the 12v fuel heater on a switch and relay. Maybe install some salvaged valves from a cars heating system to shut off flow to a coolant to fuel heat exchanger if you feel the need.

Some have experemented with their final fuel temps to find what makes their engine run best. I have only heard this a few times.

__________________
"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way".
by JerryBro

The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue

My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair

62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels