It's a combination of four factors that will clean laundry (and dishes, for that matter):

- mechanical action -> agitator, revolving drum or spray arms (in a DW)
- cleaning agent - can be water but usually it's a chemical (detergent)
- heat
- time / cycle duration

Alex

heat needs to be at teh top of the list if one is using a detergent.

the difference between say 45, 60 and 85 Fahrenheit are almost orders of magnitude in surfactant efficiencies.

mechanical action in different washer types is negligible, and more a question of not ruining clothes and most effective way to hit all surfaces so you don't end up with unwashed clumps (eg twisted sheets).

another huge factor is water hardness