quote:...the best thing is to perform a "Poor Man's Oil Analysis".
While it won't give you readings as accurate and precise as results from a lab...

Read more: http://themotoroilevaluator.co...lysis/#ixzz3j0yCbYkz

I agree this can be a valuable test but disagree with the interpretations at least slightly.
Blotter paper is nice, it need not be suspended, it can actually lay on a paper towel on a clipboard that is flat not hanging. Once there is color to the oil there will be a darker spot where the initial drop was placed but the color should be uniform to the edge of the wicked area if the detergent(s) are still adequate. As the detergents are consumed the center drop spot will become more apparent and at total failure the spot will be the only color on the sheet, the previous circle will again become mostly colorless.
I would expect the failure of the detergent to maintain dispersion to be the terminal point, you don't want to go that far. The primary "stuff" the detergent is helping to suspend or disperse are the oxidized oil and additives, out with the old and in with the new.