hot water loosens up the grease so the detergent can "grab" it. The detergent molecules seize onto grease molecules and don't let go; then when you rinse, the grease leaves w/ the detergent.

But detergent can only grab what it can TOUCH. And it can only touch the SURFACE of a glob. Hot water thins the grease out and spreads it around so that more of it is available for the detergent to grab.

(sort of like e. coli; it grows on the surface of meat, and that's why ground beef is so dangerous--more surface area, bcs every tiny piece has its own surface area; plus of course that it's inside, and it's harder to get heat to the inside of something)

That's why greasy stuff washes better in HOT water. That's why it's so important to wash sheets and towels (which get more skin oil on them) in hot water--so the grease will liquify and become available for the detergent to grab.

Also for non-greasy food (which there's not much of), heat (because it makes molecules vibrate faster) will speed the dissolving of the food.

Go heat!

Talley_Sue gives a great explanation.

I've frequently washed dishes in cold water while hiking and I've not wanted to go to the hassle of trying to heat water.

But, if anything is really greasy I'll heat the water and soap in the greasy container.

Or, I'll scour with dry sand and then wash.

Lots of things you can do in nature. :-)

When there is no enough hot water, I use cold water to wash. For oily or greasy, just make sure, you scrap your food and oily surface with tissue until the oil gone, then wash it. Easy