The Booster Fuel has 2 types: High grade and Low grade. This page talks about the High-Grade type. High-Grade Booster Fuel. High-Grade gives a temporary boost like Low-Grade. The High-Grade Booster has a duration of 19 seconds if that timer hits 0, you'll lose that Boost
If Thruster Fuel is already loaded into the Thruster it will switch to it. If not it will go dormant until another round of Thruster Fuel, Low-Grade, or High-Grade is loaded into the Thruster.
Once again, the only disadvantage of High-Grade Fuel is that Thruster Fuel lasts significantly longer than BOTH types of booster fuel.