Celia Lehrman of Consumer Reports said they looked at dishwashing liquids from big brands like Dawn and Palmolive and from large retailers like Kirkland Signature from Costco and Earth Essentials from CVS.
The most expensive product tested was the Laundress Dish Detergent, which costs close to $1 an ounce.
To test a dishwashing liquid's cleaning power, Consumer Reports created quite a mess.
"If you think your dishes are dirty, well, we actually take a mixture of evaporated milk, egg yolks, sugar and flour, smear it on glass plates, bake the stuff on, and then we try to clean it off," Lehrman said.
Testers poured warm water mixed with dish detergent onto each glass and the scrub machine goes to work.
Because many of the dishwashing liquids claim to be "hard on grease," testers checked that out, too. They dipped steel plates in lard and left them to harden. Then the plates were put into the scrubbing machine.
Consumer Reports found that all the brands that were tested performed equally well, regardless of price.
"So really, the best advice from us is just go buy whatever's on sale," Lehrman said.
Among the least expensive dish detergents were Kirkland Signature and Ajax at just 6 cents an ounce. They can make quick work of dirty dishes.
Consumer Reports offered this cleaning tip: Your soapy dishwater is good as long as you see suds. Once the suds are gone, you've lost your cleaning power, and that means you need to start over with new water and dishwashing liquid.