ok, so i'm going to turn my 6.2 diesel k5 into a veggie oil truck and i've been considering ways to heat up my fuel tank so that i can decoagulate the veggie oil. so far i've come up with two concepts. the first would be to run coolant down the heater core lines which would run to copper tubes which would run through the tank. i would use maybe 5 copper tubes and drill a total of 10 holes in the tank - 5 on either side of the width of the tank. Then i would connect the tubes w/ rubber lines and run the final rubber line from the copper tube back to the heater core. the second concept would be to take smaller diameter copper lines and silver solder them to the outside of the tank. i would use many feet of copper line to increase surface space. Then i would insulate the outside of the tank and lines to direct the heat from these lines into the tank. Again i would use the coolant lines in parrallel with the heater core. Which idea is better? I was thinking the first would be best for quick heat up times, but i don't know if i like the the idea of running coolant actually through my fuel tank. Given the nature of offroading it needs to be very tough. I do however, think this is a sturdy way to do it which would not have much potential to crack and allow coolant into my fuel. Also, I would need another small tank to start my truck on diesel while the fuel heats up, and end it on diesel to purge the lines of veggie oil which might coagulate. Where would i connect the fuel lines so that I prevent coagulation prior to this connection which might prevent easy flow of the veggie oil? Thanks!