> I wonder how much this really matters. For me my dishwasher is far enough from the hot water heater that it generally takes several gallons for the water to run hot.

(I'll preface this with: If your dishes are coming out clean and you're happy with them, then keep on keeping on. The reason there's a lot of discussion around this is because there are a lot of people who _aren't_ getting clean dishes out of their dishwasher.)

If you listen to your dishwasher's cycles, you'll probably hear it do a relatively short initial rinse to get off the bulk of the gunk, then the main wash, then another rinse. (Maybe multiple washes/rinses, but that's the general pattern.)

The idea is to make that first rinse most effective. Anything that can be taken off in the pre-wash cycle is something that won't be washed off in the main wash and cycled over the dishes over and over.

As people normally use their dishwasher, that cycle is being done with cold to lukewarm water and no soap. Most people wouldn't see a oily plate with dried-on sauce on it and think to clean it by spraying it in the sink with cold water until it were clean. But that's what the dishwasher's doing to their dishes.

Hence the suggestion of running the hot water tap first. It's a very easy thing to do to ensure the dishwasher's using hot water in that initial rinse and everyone generally accepts that hot water's going to dissolve and rinse off the food and oils better.

Another very easy improvement is adding a bit of soap to the basin. Most dishwashers only have a single compartment for soap and it's released during the main wash. If you throw a squirt/scoop of detergent into the basin before you start it, that will get mixed in to the pre-wash cycle.

The cycle's happening anyway, using hot water and soap is just making the most of it!

Anecdotally (like all these other comments), my wife's approach is definitely the "racoon on meth" archetype--throw the dishes wherever they could fit, throw one of those detergent pods in, hit "start", close it, wait a few hours, then take all the dishes out and dump water out of cups and bowls and handwash them because they're still filthy. When I was building the kitchen, she was questioning the expense and effort of the dishwasher because in her entire life she's never had one that actually cleaned the dishes properly and thought they were kind of pointless.

Since I didn't want to spend the next however many years hearing about how the dishwasher sucks, after we put it in I played dishwasher czar for a month. I loaded the dishes properly, put in the proper amount of soap (and a sprinkle in the basin), made sure the rinse aid wasn't empty, ran the tap first, ran the dishwasher. Every single load came out spotless. She'd often question something I was putting in because "there's no way it's going to get that off". It did. Every time.

Wife satisfied that the dishwasher is good and having had a month of instruction I unleashed the meth-y racoon on it, and we're back to the dishwasher being a really elaborate rinsing machine we use before handwashing the dishes.

Is it just the running the tap? Probably not. Just like it's not _just_ the adding soap to the basin, using the rinse aid, loading them properly, etc. They all contribute to "using the dishwasher most effectively".