This came across my mind the other day about taking UOA's. On my Harley, there is a 'system' you can buy to run all the old oil out of the system during an oil change. It involves the use of a filter block and is a screw on 'cap' that fits where the oil filter is, and simply reroutes the oil right back into the engine, unfiltered. The basic premise of this kit is to remove the 1/2 quart of oil oil left on the dry sump system, for those that cant stand the thought of 1/2 quart of dirty oil mixing with new oil. Anyhow, it got me to thinking. If one wants to do a UOA, are the results not skewed a bit by the oil filter removing particles out of the oil? Would using something like the 'fake filter' cap actually give you a more realistic engine metal portion of the test due to no filtering of the oil?