It seems the most useful thing I can pass on is regarding inline electric wvo heaters. These are simple to make using off the shelf plumbing components for around $15 each. If you are good at salvaging they can be made for far less.
They use a standard 240vac water heater element run on 120vac. Since oil does not “dissipate” heat as well as H2O if 120vac elements are used or 240vac elements are powered with 240vac they may not last as long before needing replacement. I have never burnt out a 240vac element yet. These may be salvaged from discarded water heaters since the upper element is nearly always good even if the lower element is shot. Most often they are both good and the water heater has been discarded due to sediment buildup of a leak in the tank. If you do salvage the elements try to also salvage the adjustable thermostat(s) as well.
The inline heater cartridge is made by screwing the element into a standard 1″ copper female threaded pipe fitting, cutting a length of 1″ copper pipe that is slightly longer and drilling 2 holes in this pipe into which will later be soldered an inlet and outlet copper pipe of the same size as your fuel line. These holes are drilled about 1-1/2″ from each end of the pipe. By simply soldering the copper inlet and outlet pipes, the end cap, and the female threaded fitting together and screwing the element in the open end you have a simple and effective inline wvo fuel heater. By adding a foam pipe insulation cover and cutting out a rectangle the exact size of the adjustable thermostat then using zip ties to hold it all together you have an adjustable inline heater. I usually add a second layer of larger foam pipe insulation on the outside of this leaving just a small viewing hole so I can adjust the thermostat if I need to. If you need a higher capacity heater use a higher capacity element. Remember…a 3000w 240vac element only draws 1/4 that amount of 120vac, so it is really the equivalent of a 750w 120vac element. That should be plenty.
Similarly a water heater element can be used to slightly warm your fuel tank. If you want to weld in a 1″ Female NOT fitting into the bottom of your fuel tank it can be set to warm the fuel to get it to flow if it is too viscous. Of course you will want to insulate the tank to conserve energy. I have found that discarded cardboard from large boxes is a cheap and durable insulator. By cutting widths that match the width of your tank and taping layers on with duct tape you can create a much better alternative to fiberglass. Even just a few layers makes a great difference. As I think I mentioned before free water can encourage microbial growth. Free water and warmth are an even worse combo. And strangely enough water can drop out of wvo long after you think it is dry. So don’t forget to drain any water off the bottom of the tank regularly or use a biocide if you are storing wvo for more than a few months.