I had the bright idea to wash my underhood wiring harnesses in the dishwasher to remove the 4+ decades of grease and grime. After two runs, they are still not much cleaner than when I started.

I'm thinking dishwashing detergent isn't the best thing to cut this type of grime. I fear using the wrong soap and finding my kitchen knee deep in soap suds too.

Has anyone perfected this technique, or should I just scrub the things clean by hand at this point?

Thanks!