If you wonder why dishes come out of your dishwasher with bits of food still stuck to them, it could be because you’re rinsing them first. It seems counterintuitive, but prerinsing can make your dishes come out dirtier, not cleaner. That goes for glasses, pots, and silverware, too.

The reason is that most dishwashers costing $500 or more sold in the past five years or so have a sensor that determines how thorough a wash is needed. At the start of the cycle, it rinses the dishes and then checks how dirty the water is to determine the proper amount of time and water to get everything clean. If you’ve already rinsed off much of the muck, the sensor misreads the dishes as already fairly clean.

When that happens, the dishwasher gives them just a light wash, and items come out less than sparkling. To avoid that lackluster result, don’t rinse; just scrape off bits of loose food. And use one of the detergents that did best in our dishwasher detergent tests.

Dishwashers to Consider

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Editor's Note: This article also appeared in the May 2016 issue of Consumer Reports magazine.