Mini-rotary viscometer

The mini-rotary viscometer is a device used to measure the pumpability of an engine oil at low temperatures.[1][2] Engine oils must meet viscometric standards including those determined by the MRV in order to be classifiable within SAE J300 viscosity grades. The requirement was added after the winters of 1980-81 and 1981-82 caused major pumpability field problems in the US and Europe.[3][4]

Different MRV test procedure exist; for example ASTM D4684, required for SAE J300, involves heating the oil to remove its "memory" then cooling it at a controlled rate over a period of more than 40 hours to the test temperature.[5][6][4] ASTM D4684 is done with fresh oil, so the MRV result may not be representative of used oil pumpability.[7] Some motor vehicles manufacturers specify used oil MRV requirements.[7]

References
  1. H. Shaub; M. F. Smith; C. K. Murphy. STP621-S4 Predicting Low Temperature Engine Oil Pumpability with the Mini-Rotary Viscometer. ASTM International. doi:10.1520/STP27339S.
  2. admin (2015-08-08). "How to achieve "real-world" fuel economy gains from your viscosity modifier". F&L Asia. Retrieved 2020-12-03.
  3. Stambaugh, R. L. (1984). "Low Temperature Pumpability of Engine Oils". SAE Transactions. 93: 94–101. ISSN 0096-736X.
  4. Selby, Theodore W.; Miiller, Gregory C. (2008-10-06). "Thermal History of the Engine Oil and Its Effects on Low-Temperature Pumpability and Gelation Formation". Warrendale, PA. Cite journal requires |journal= (help)
  5. "YIELD STRESS AND APPARENT VISCOSITY OF USED ENGINE OILS AT LOW TEMPERATURE: ASTM - YONGRUN". www.dgaequipment.com. Retrieved 2020-12-03.
  6. https://www.tannasking.com/documents/17/MRV_TP-1_Brochure_2019-01-08.pdf
  7. member, Michael J. Covitch STLE (2007-04-01). "Lubricant Additive Effects on Engine Oil Pumpability at Low Temperatures—Detergents and High Ethylene Olefin Copolymer Viscosity Modifiers". Tribology Transactions. 50 (1): 68–73. doi:10.1080/10402000601105540. ISSN 1040-2004.
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