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When it comes to mixing, turbulent flow is desired within the mixing vessel to create ideal mixing conditions. Some highly viscous materials have a viscosity of hundreds of millions centipoise. For comparison, water has a viscosity of 1 cP while honey has a viscosity ranging from 2,000 to 10,000 cP. Low viscosity materials, such as water, have a lower resistance and flow more rapidly whereas high viscosity materials, such as honey or tar, resist deformation and flow more slowly. Viscosity is a measure of how resistant a fluid is to flow and is measured in centipoise (cP). Viscosity is one of the properties that influences how easily a mixture can achieve homogeneity. Given the focus on greater fuel efficiency and reduced greenhouse gas emissions, it is realistic to expect OEMs to continue to target the introduction of new performance specifications below 2.9cP without compromising engine protection.įor more information on HTHS engine lubricants, contact your Lubrizol representative.Homogeneity of the final blend is a critical aspect of mixing as uniformity impacts the final product in many ways such as stability and durability. New additive technology in combination with performance polymers and performance base oils is essential in enabling the move to low HTHS viscosity formulations to meet the latest OEM performance requirements and provide value added fuel saving opportunities to the modern commercial vehicle fleets. Moving to high performing low HTHS viscosity engine lubricants is complex.
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Other OEMs have also introduced low HTHS viscosity specifications to cover specific on-highway diesel engines including Cummins CES 20087 and Detroit Diesel DFS 93K223.
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Backward compatibility exists on specific engines, allowing fleets the opportunity to benefit from fuel efficiency gains from their existing vehicles. As well as having increased durability protection requirements, the specification has more stringent fuel economy limits along with the requirement to meet the API FA-4 approval with a HTHS viscosity of 2.9-3.2 cP. Mercedes-Benz was one of the first European OEMs to introduce a low HTHS service-fill specification, MB 228.61. The ACEA introduction date is expected to be in 2020. These new categories will be low HTHS viscosity variants of the upgraded ACEA E6 and ACEA E9 categories respectively and will have limits between 2.9 and 3.2 cP in line with API FA-4. Given the increasing drive to lower HTHS viscosity lubricants by European OEMs, two future ACEA fuel efficiency categories have been proposed, potentially called ACEA F8 and ACEA F11. The API FA-4 fuel efficiency category requires lubricants to pass the same performance tests as API CK-4, with the addition of a HTHS viscosity limit of between 2.9 and 3.2cP, to deliver increased fuel efficiency benefits whilst maintaining engine protection. New API CK-4 lubricants must pass more stringent oxidation and aeration limits with increased shear stability, providing greater protection for heavy-duty diesel engines. How Industry Specifications Have Evolvedĭuring the 2016 category upgrade, API CK-4 was introduced to reflect the upgraded performance benefits beyond API CJ-4 for engine lubricants with a minimum HTHS viscosity of 3.5cP. This resulted in the introduction of API FA-4 as the first fuel efficiency category with first licensing from December 2016. The formal requirement for more fuel-efficient heavy-duty engine lubricants has been on the horizon as far back as 2011 when OEMs requested a new category be introduced by the American Petroleum Institute (API). Original Equipment Manufacturers (OEMs) are moving to lower high temperature high shear (HTHS) viscosity engine lubricants for their latest engine hardware designs to deliver greater fuel efficiency.