Ah MT, there is a lot more to how you clean microfibre cloths than simply throwing them in the washing machine, setting the temperature, spin speed and adding some detergent and switching the machine on while you sit back and let it do its thing, well, if you want to look after your microfibres and get the best out of them, that's what I think anyway.
When I wash microfibre cloths I don't put them in the washing machine unlike others have mentioned, firstly because I don't want detritus and dirt from my motors as well as car products going into my washing machine that is used for our own clothes and what have you, and secondly, because I believe there is a better way to wash them to prevent damaging the fibres and extending longevity.
The way I do things is to divide my cloths into 4 piles all are clean and dry, but they may carry residual 'staining' following use if you get my drift, so the 4 separate bags I keep contain the following:
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I see those dishing out the advice haven't really made things crystal clear to my way of thinking, not particularly intellectual to say "Do you have a washing machine?" or helpful even, when asked for further clarity to simply add "Everything thing is 30 Deg C and 59 minutes when I use the machine". Further more, in my humble opinion not only is this woefully lacking in information but it is I believe way off kilter, the member might have benefitted from getting some help from AI to give a more comprehensive post perhaps, anyway, I will explain things in more detail here for you by giving an idea of the way I do things and why, so here we go then ...
I wash all my microfibre cloths by hand: if they are lightly soiled they probably don't need to be soaked first, but if they are very dirty and heavily soiled, I will soak them over night ready to hand wash the next day. After being hand washed they are thoroughly hand rinsed in clean cold water. If the cloths are grossly soiled they go in the bin and if they dry out and end up being course or too firm to the touch these will also go in the bin.
I never, but never use any fabric softener with my Microfibre cloths (MC). This has been mentioned above, but no reason as to why has been given so I will offer that up to you here.
Fabric softeners are designed to leave a silicone like residue over fibres which is fine on other fabrics but in the case of MC, they can clog up the gaps between fibres, thus reducing the efficacy of the cloths to draw up liquids and trap dust particles which is the very reason we like MC so much.
The same silicone-like coating will also reduce the potential for electrostatic charge occurring on the MC fibres which will again reduce efficacy in its ability to attract and hold onto dust and dirt, while the additives ... enough already before I get accused of being AI again, or lacking in intelligence etc., so if you want any more detail, on the effects fabric softeners have on MC you best do a search for yourself, sorry and all that,
This is what I use to wash my microfibre cloths with:
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Now you might be thinking a Bio laundry liquid would remove more stains from the cloths and you would probably be correct, but there is a price to pay and that is likely to be the integrity of the microfibres themselves, so that's why I go for the non-bio version myself.
The problem being Bio detergents contain enzymes like protease and amylase which break down organic stains, all well and good for ordinary materials, but there becomes and issue when the synthetic microfibres have trapped the waxes and oils etc. of car products which attract the enzymes and end up causing the fibres to prematurely wear. The MC demonstrate this as they become seemingly less absorbent, or grippy as it were, and don't pick up the dust when used to dry wipe surfaces like they once used to. Yup, that's it for this bit like I said before don't want to be accused of being AI or just 'A' so for more info on the pros and cons of the detergents regarding MC, and which is best to go for, a quick search should bring up plenty.
So then, the next really important thing is, how you go about drying the microfibre cloths!
This is my advice and equally importantly why:
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Don't hang them outside or on the line to dry - drying the MC outside has a high risk of them becoming contaminated by various things carried in the air, from dust, pollen, vegetative debris to animal and insect excrement etc. Drying in direct sunlight can not only fade MC, but it can stiffen the fibres too.
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Don't dry them in a tumble dryer - the heat can alter the polyester structure, mechanical damage can occur even on a cool setting as friction occurs between the cloths rotating in the drum damaging the fibre leading to clumping or fraying, and it can flatten the pile in high pile MC. etc.
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Do allow them to air dry inside, but not in a confined space: hang the MCs inside but not in a confined space or where there is a lack of air flow like an airing cupboard.
So then, I dry my MC in the conservatory with the blinds on one side closed so they are out of direct sunlight and air born detritus, they are spread out on a clothes horse, and are turned intermittently. Thus my recommendation is for something similar i.e. air drying inside somewhere like a utility room or conservatory for maintaining microfibre integrity whilst reducing the risk of airborne contamination.
Last but not least, once dry, give the MC a good shake out to re-fluff up the fibres, encourage any loose fibres to drop away and to rebuild electrostatic charge, now fold and store appropriately.
about as complicated as Micro fibre cloths, what size, how many parts per million, colour. Christ, I can see this one running to another 10 pages of tips/comments 
but several members have been keen to keep me updated 
Only thing I can't stand is cleaning microfibre cloths when finished
