The Z17 Muscle Coalescer has a hold time of 15 minutes, and with its coalescing media, will be able to separate tramp oil which naturally gravity separates in 20 minutes or less. To determine the amount of tramp oil that will naturally gravity separate in 20 minutes, you will need to take a miniature separation test for each sump. Using a clean, clear plastic pop bottle, for instance, dunk it in from the top of the sump to the bottom, for a cross section of the solution. Cap the bottle off and shake it vigorously for 10-15 seconds. Then let it stand to naturally reject the tramp oil while timing the process. Whatever tramp oil separated in 20 minutes will be the amount that the Muscle will be able to remove from that sump. To note, as coolant ages, and the more base oil there is in your coolant, tramp oils will take a longer time to gravity separate. You may find that older sumps take longer for the oils to separate. However, if you were to use the coalescer from the first day of a recharge, it will remove the tramp oil effectively. Also, add on high-pressure coolant delivery systems cause tramp oils to deeply emulsify into the base coolant because of the pressurization of the solution. During the separation test, you may see mostly a separated inverse layer, somewhat like a milkshake. This may be the only separation, yet this layer is still best removed. If using a coalescer, it is recommended to run the coalescer only when the machine pumps are not operating, whenever possible, for the best effectiveness.