Which fuel do generic 2kn thruster needs

[berkekrkn]

This black engine is Generic 2kn thruster. I've built the same thing in this picture. I'm also using real fuels. But when I right click on the fuel tank it should normally suggest me the sort of fuel but for this engine nothing is suggested. 

 

But this guy in post can get 3.400 deltaV from these engines. Do you have any suggestions ? Also can you suggest me small pressure feed engines mod for ksp RO except rla stockailke

[NathanKell]

You need to set the engine config of the thruster to whatever set of propellants you want. Like RCS, there are many options. Then you need to change the tank type to one of the highly-pressurized types (ServiceModule or Fuselage).