anything will cause swirls or scratches if not rinsed or if the wash water gets dirty...

more good info on the wash process:
http://autopia-carcare.com/autopia/inf-wash.html

and a great article on micro fiber (he has a note about not using mf as a wash mitt towards the end):
http://www.bettercarcare.com/articles.php?articleId=44

here is dave bynon's opinion:

"BIGGEST LOSERS
I

 

I use MF wash mitt
I use MF bonnet on my PC to remove zaino

You will find many owners have switched to MF towels instead of 100 % cotton. why ? MF works much better.

 

I went to costco this past weekend got 12 MF towels for 8 bucks

 

Pakshak towels are the best.

I have the yellow MF from Priceclub as well. It does the job but does leave some lint behind. It is not lint free. I *just* washed them today, hopefully that's all they needed.

 

Not all MF's are created equal. Take an old CD and rub the back with it. If it leaves scratches then i wouldn't use it.

 

I've been using the same MF towels for about 6 months and wash them after every use. I was wondering if after a certain amount of washes they lose their quality and it's time to replace them? They still do a good job with removing wax and drying the car, but I'm concerned that maybe the towels lose strength and may scratch the surface.

 

as long as you dont use heat on them, and wash them separately i find that they seem to last forever...
as they get dirtier (when washing doesnt get them really clean), i no longer use them on the body- but use them for underhood, wheels, and undercar cleaning. i use only really clean ones on the paint.

 

Pakshak