Well one day it was getting low I poured a new bottle in and all the dishes weren't getting washed. I called the detergent company to report a defective bottle, but turns out there was some sort of formula change due to a new regulation. Apparently mixing the two together in the auto-dispenser causes them to harden and clog the dispenser. So I tried just pouring it into the manual dispenser, slightly better but the dishes weren't really clean. I called my dishwasher repairman who just told me to buy Finish tabs and we would be fine.
My mother called me weeks later saying that six of her tenants complained that their dishwasher was broken and she had already replaced one (two of the dishwashers were less than two years old). I told her to just gift them all a tub of tabs from Costco which worked.
The new fluid by itself was fine, it was just the combination of the two that created a reaction.
More of an issue for newer cars though, I will give you that.
Less shipping cost/environmental impact too.
30 litres for around £7 (plus a few pennies for water) doesn't seem bad to me.
My anecdata based on “feedback” I’ve received over the years:
(1) Greasy and sugary things will go through fine.
(2) Proteins, like supplements, eggs, less cooked meats or cat food, tend to denature more and get stuck/baked to dishes to the point of needing a rewash.
(3) An exception is proteins in a fat emulsion (like mayo) where fat has a stronger influence on the properties of the residue.
This is after trying multiple tablets, even ones that promise pre-wash free dishes, in a pre-Energy Star dishwasher.
It should be only slightly more difficult than removing lint from the dryer.
Proteins are softened and loosened by soaking in water. Many glues are protein-based and, for that reason, protein-glued items should not be exposed to high humidity or water. For example, most violins are glued with animal hide/hoof or fish protein glues.
Soaking protein in plain water will eventually loosen it completely. The process is reversible: drying re-hardens the protein.
An ideal dishwasher would let you load it up over a day or too, and keep the dishes moist but intermittently misting them. Probably terrible for mold and mildew however.
The same is true for washing machines in laundry, running them without detergent will still remove some stains.
With the extra rinse, I've never had any kind of buildup of detergent in the machine. I know this because I wash my shower curtains with just water and bleach every ~month to remove mildew, and there are zero suds.
Then again I have one of those small half size ones that look like a cabinet door.
I do this with the same set of plate(s) and utinsils and rice cooker it's great.
Granted, I cook daily for myself, and I steam everything and avoid oils/grease in general with chicken/fish.
But it's possible, the only issue I have is hard water stains but better than scrubbing it with a sponge.
I do put soap in but he few occasions I forget I don’t worry and put them away anyway.
Now, maybe he was making it up. But i suspect that there is a common class of dish dirt where prolonged steaming and jetting with hot water is adequate in practice - i'd expect anything water-soluble to dissolve in hot water! So, residues from tea or coffee, water-based pasta sauce, fruit juice, jam, etc. It won't work for everything, of course, but it might work for a surprising range of things.