5.1 The cloud point of petroleum products and biodiesel fuels is an index of the lowest temperature of their utility for certain applications. Wax crystals of sufficient quantity can plug filters used in some fuel systems.

5.2 Petroleum blending operations require a precise measurement of the cloud point.

5.3 This test method can determine the temperature of the test specimen at which wax crystals have formed sufficiently to be observed as a cloud with a resolution of 0.1 °C.

5.4 This test method provides results that are equivalent to Test Method D2500.

Note 1: This is based on the Test Method D2500 equivalent cloud point in which the 0.1 °C result is rounded to the next lower integer.

5.5 This test method determines the cloud point in a shorter period of time than Test Method D2500.

Note 2: In cases of samples with cloud points near ambient temperatures, time savings may not be realized.

5.6 This test method eliminates most of the operator time required of Test Method D2500.

5.7 This test method does not require the use of a mechanical refrigeration apparatus.

Note 3: In certain cases of high ambient temperature, a source of cooling water may be required to measure low temperature cloud points (see 7.1).

1.1 This test method covers the determination of the cloud point of petroleum products and biodiesel fuels that are transparent in layers 40 mm in thickness by an automatic instrument using a constant cooling rate.

1.2 This test method covers the range of temperatures from −60 °C to +49 °C with temperature resolution of 0.1 °C, however, the range of temperatures included in the 1997 interlaboratory cooperative test program only covered the temperature range of –56 °C to +34 °C.

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.