1.1 Method A
A sample of used lubricating oil and normal pentane are mixed and centrifuged. The up-layer oil solution is poured out slowly; the deposit is washed twice by normal pentane; after drying and weighing, the normal pentane insolubles are obtained. During determination of toluene insolubles, another sample and normal pentane are mixed and centrifuged. The deposit is washed twice by normal pentane; once by toluene-ethanol solution and once by toluene again. Then dry undissolved substances and weigh; toluene insolubles is obtained.
