[brownbear]

the method with the lines looks good. I would then get the whole lot stuffed down a pipe or such to protect them. I thought if you used shop vac hose 2.5 inch or pvc pipe it would house them under the body nicely.

the thermometer on the injector might not give the whole story your after. The diesel will also be getting some heat off the IP. So it might not show the whole thing. As the engine will be transmitting a lot of heat to the head too.

I would instead put it on the fuel line going into the IP. The one after the 3 port valve. This way it will tell you the temp of the veg oil going directly into the engine.

try it the way you are thinking thou, I very interested to see if that indicates like your thinking.