One of the functions of the diesel return is cooling of the fuel, so I am told.
As you heat diesel, you diminish its lubricating qualities. Clearly an experiment which seems unlikely to have favorable results.
I have my inline electric heater right before the IP, with a switch that turns it off when on diesel, of course. My coolant heating remains exclusively on the veg side. If I ever were to put diesel in that tank, I would put simple ball valves in the coolant lines. If you can do this is dependent on your plumbing situation.
Heatings blends is a whole different realm of experimentation.....
Document your triumphs and failures so we can all learn from it.
