While testing in creative, which fuel are the best in the immersive engineering diesel generator, i found that:

• any fluid, (ex.: water, milk, tree oil, etc.), if inserted into the generator, even only using IE pipes and tank, causes the generator to infinitly output energy WITHOUT consuming the fluid
• if the above case happens, the generator does not play any animations
• the following fluids had no issues:

• -biodiesel from IE and pneumaticraft
  

• -creosot/ creosot oil from railcraft, gregtech, thermal and IE
  

• any amount of other fluid caused the infinity energy behaviour, pl.: 450 mb, and it was still not consumed
  I will also submit this to the IE-s Github too

BluSunrize/ImmersiveEngineering#5870 , Fixed in mod dev, not yet released to 1.20.1 by the mod developer