That book, "From the Fryer to the Fuel Tank," is great nostalgia, but old, old news. Veg oil systems have come a long way since then. Check out the great diagrams on the infopop board...
Looped returns cut down on amp draw, if you are pre-heating electrically. The most important thing, imho, is the oil temp when it hits the IP. Tank warming takes a back seat to that, and coolant is a superior way to do that.
I'm gonna loop the return, with the solonoid, so I am never looping hot diesel.

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)