No way I'd try that. A pressure washer has (duh!) lots of pressure, and that pressure can force fluid through otherwise tight seals etc.
If it's that dirty, I'd mix a weak soap solution using Dawn dish soap or similar. Rinse with low pressure clear water first to get rid of grit that can scratch stuff, then apply soap solution with a soft brush or microfiber cloth. Finish by rinsing with clear water and then dry with microfiber cloth or one that is damp and wrung out, as that tends to absorb water better than a completely dry one.