[rheavn]

It is not specified how much of the cleaner is used in the presoak. By the photo of it being sprayed on with a common hand sprayer, it doesn't appear you would use too much. The fluid is $23 a gallon. Below is the cleaning instructions.

http://www.knfilters.com/instructions/19069_inst.pdf

I spoke with K&N tech support. He stated he didn't think you would use more than a quart of the cleaning fluid each cleaning, with a normally dirty filter. You want to coat the surface, but not trying to get it dripping wet. He also stated that they recommend cleaning the filter when the filterminder rises 15 points from where you start with a new filter. He also stated that each cleaning would take away a small amount of longevity. He stated the 300,000 miles and 10 washings is an estimate from the feedback they have received from units in the field. Your results may vary.