Part of our adventures making minimum viable transport ships. This thing barely works, moves slowly, can't fire at many asteroids, only sorta supplies enough energy. It gets where it needs to eventually though and includes the most important space ship feature: Blinky lights
Well sorry for sending you down this rabbit hole, but thrusters get more efficient the less fluid is in their internal reserves ;)
There's a table on the wiki page detailing how internal fluid reserve impacts thrust and efficiency.
I've omitted the fuel tanks in my newer designs. Tweaking the chemical plant output with modules is an easy way to hit the desired efficiency point. Although it's probably not that easy when you have only one single shared chemical plant.