I pulled my driver's side maxpider kagu out of my car when I washed it in cold temps yesterday. The mat was completely caked in magnesium chloride due to the horrific amount of snow we've gotten in my part of Colorado this year.... consider also that I just washed it four weeks ago.
It cleans up pretty good though, I just gave it a douse of foam from my foam lance that I used to wash my car and then blasted it with a 25 degree power washer tip and then let it drip dry and it looks pretty close to new.
I have found one disappointment with the mat which is that the coverage does not go far enough up on the driver side near the accelerator pedal location. The carpet on my five month old car is already noticeably worn in that spot, assumably from where my size 11 boot rests a bit while I'm driving the car. It would be nice if the mat extend up a few more inches there to protect the interior carpet.
I will hack a solution, probably just cut to fit a piece of Velcro and stuff it in there so the carpet does not get completely worn through over the next few years. Kind of disappointing that a $60,000 car has such cheap interior carpet that it's wearing out in five months in spots. Never a problem in any of my other cars unless I kept them for many years.