I chose a different approach … use less soap 
I don’t use a rinse agent, I use about 1/3 to 1/2 of the recommended detergent amount and I use the “sanitize” mode of the dishwasher. I do pre-soak/pre-rinse all my dishes in hot water to get rid of any solid left over food before putting them in the dishwasher.
Funny, I’ve been experimenting with using less soap. It seems to work just
fine and doesn’t have (or less so) that detergent smell (scent added to the
detergent).
I like my “soap test” for dishes. Just take a tall glass from your shelf and put it under a lot of warm running water. fill and flush several times. then dry the glass. This is to prepare a clean “reference” glass.
Take a second glass, freshly washed out of the dishwasher, preferably same size and shape as the “reference” glass. If glass is still wet from dishwasher, let it dry.
The test:
Using cold tap water with the valve open as much as possible, fill each glass to within 1 cm of the rim. Do not let the water overflow or spill out of the glass. The idea is to fill the glass with turbulent water so the water picks up any residue left on the glass and the air bubbles in the water will float up to the surface. Now compare the duration of the foam on the surface of the “clean washed” glass against your “reference” glass. There should be little difference if your dishes are truly clean.
Reduce detergent until you are satisfied with the results.
You will notice that if you use rinse-agent, the foam actually lasts longer.
I just read that the purpose of the rinse-agent is to facilitate drying of your dishes after the wash, not to remove soap from the dishes during the rinse cycle. I have not experienced any issues with drying, however I do open the dishwasher door as soon as it is finished and pull the trays out. Sometimes I give things a shake if they have a pool of water on them (like coffee cup bottoms)
Interesting! I’ll give this a try.
I like your test, I’ll give it a try with the next load. To get rid of the
extra soap, I’ve typically been running a second rinse cycle at which point
the items no longer have the artificially scented detergent smell.
I’ve started using washing soda for dishwasher detergent. A 3kg box is about $5 if you can get it on sale.
So…more economical than buying dishwashing powder. I use about the same amount or less than a commercial brand I’ve used in the past.
Seems to work well. Not noticing any film on the dishes. There is a rinse agent in the dishwasher but when that runs out I’ll try vinegar.
I buy washing soda anyway to make laundry detergent. The laundry detergent is definitely not cost effective, but I make it because of allergies to commercial detergent.
Hey! Washing soda is on sale right now at London Drugs.
I had to revert to regular dishwashing detergent as the pure washing soda wasn’t cutting it. I have settled on a really good homemade laundry detergent if anyone is interesting here it is:
1 5oz. bar castile soap
1 cup washing soda’
1/2 cup baking soda
1/2 cup citric acid
1/4 cup coarse sea salt
Grate soap and mix with other stuff. Use one to 2 tablespoons per load.