How hot does the oil need to be? All my research indicates that 160*-180* is optimal. This is slightly lower than coolant temp in most engines. So if you are running a coolant heat exchanger to heat the WVO and the WVO temp leaving the heat exchanger is at least 160* (likely it will be hotter) right before it hits the IP why would running a loop have any benefit? The "WVO solidifying and clogging the lines" in the return system is not a problem. If you are running the simplest HOH system you already have two coolant hoses, a feed and a return to heat the tank and the WVO feed line. Adding a second WVO return line to the HOH bundle will keep the WVO from solidifying and also add its heat to the bundle of hoses to heat up the WVO feed line. Simple. RT

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