I'm not sure of the amount you would use for a regular washing machine, but, experiment with it. I also do not add any essential oils for fragrance nor do I really know if you can. Again, if you want fragrance, experiment until you find a balance you like.
I've started making my own detergent for a few reasons, but, one of the main reasons besides being cost effective is that it is all natural and will not hurt your septic system. Plus, borax is great with other household cleaning. Nothing puts a shine on your throne like good old borax.
Who say's it ain't grand to be the king?? ;-)