This is from a website powerstop.com
DOT 4 is used in some euro and domestic vehicles. DOT 4 Plus is used in Mercedes and Volvo. DOT 4 Low Viscosity is used in some BMW models. Finally, DOT 4 Racing usually has an added blue color.
Just be certain you are using a glycol based fluid. I suspect the plus has some additives. NO silicone. It is best to use a pressurized tool to force the fluid through the system; Something like Motive Products POWER BLEEDER model0100 for European cars.