This is simply the only way to do your air filters.
Each time you clean them they are like new again.
The oil is bio-degradable and comes out easily with the soap powder provided. (dont know if it is anything special, or not)
Once I remove all of the oil from my 5 or so filters, I throw them in the washing machine and they come out like new every time.
No gas or solvents no stinky hands, + because there are no harsh solvents the glue that holds your filter together doesnt harden and seperate after 5 or so uses.