In doing research for a prewashing quilt fabric for my website, I took a visit to the quilt store and checked the ends of bolts.
I was shocked to find that the manufacturers are recommending (on the bolt itself) for most quilt fabric to be washed in COOL water...sometimes lukewarm...lots marked with "Use a Delicate Cycle". There were even a couple of bolts that stated in black and white...DO NOT IRON...don't iron quilt fabric. Obviously some man in an office came up with that one.
So I pretty much always wash in warm. I figure if washing in warm changes the fabric too much, then better to know before I put it in a quilt and someone else washes it.
Julie