The answer to 'why is my pressure washer greasy' is that a greasy pressure washer is often caused by oil or grease buildup in the pump or engine. This can happen over time as the pressure washer is used, especially if it hasn't been properly maintained. Symptoms include a greasy, oily film on the exterior of the pressure washer and decreased performance.
To fix a greasy pressure washer, you'll need to disassemble and clean the pump and engine components. This may involve flushing the system, replacing worn seals or gaskets, and cleaning or replacing the oil. If you're not comfortable doing this yourself, it's best to call a professional pressure washer repair technician to service the unit.