Ok, now I'm sure pretty much all of the people out there are washing with cold water and certainly the manufacturers know this and their products are formulated to work with cold water.

I have no outdoor faucets at my place and hook up to an inside tap where I have temp control. Should wash/rinse only be done with cold water? I've been using luke warm with the idea that even a little heat helps to clean things - luke warm, tepid even, not hot.

Any opinions?

I don't think it matters. What does matter is the temp of the car. If the metal is hot, that is not good.

Some of the Optimum No Rinse users over at Autopia actually prefer using warm or hot water for indoor/outdoor rinseless washing; I don't know if they do it this way for better results or for the comfort of the user. I tried ONR in warm water this past weekend and was satisfied with the results.

As for washing with a hose and car soap, as beshannon said, be careful not to splash cold water on a hot surface and vice versa. Sudden expansion or contraction could be bad for the paint, metal, or glass. It's another good reason to wash your car in the shade instead of in direct sunlight.

Self serve washes use fairly warm water, i'd say it is better. Though too hot and I am sure it would make it easier to strip the wax, something to keep in mind.

i was my car year round.. and i use "warm" water for my mit so my hands don't freeze off!