Varnish formation remains one of the most persistent and costly reliability challenges in lubricated equipment, particularly in turbines and high-performance hydraulic systems. This session provides a practical introduction to varnish—what it is, how it differs from sludge, and why it forms—while addressing common misconceptions within the lubrication industry.

Attendees will explore the mechanisms of varnish formation, including the role of oxidation, temperature, oil chemistry, and contamination. The session also examines the long-standing myth linking modern Group II base oils to increased varnish risk, supported by accelerated oxidation testing data. Finally, participants will gain insight into how deposits form in real equipment, how temperature and operating conditions influence deposit location, and which diagnostic tools can be used to assess varnish potential before failures occur.

Key Takeaways

1. Varnish is chemically and physically distinct from sludge
   Varnish consists of insoluble, hard deposits that behave differently from sludge, requiring different monitoring, prevention, and mitigation strategies.
2. Modern base oils are not the root cause of increased varnish formation
   Accelerated oxidation testing demonstrates that Group II base oils actually delay varnish formation compared to older Group I oils—the issue lies in operating conditions, degradation pathways, and system design, not base oil type.
3. Temperature, degradation mode, oil chemistry, and contamination drive deposit formation
   Understanding how and where deposits come out of solution—especially in cooler zones, high-load areas, and precision components—is critical for controlling varnish and protecting equipment reliability.

Sanya Mathura is the Founder & CEO of Strategic Reliability Solutions Ltd and external steward of the Equality, Diversity & Inclusion Mainstreaming Committee (EDIMC) of UWI’s Department of Electrical and Computer Engineering. She works with global affiliates in the areas of Reliability and Asset Management to bring these specialty niches to her clients. She has a strong engineering background and continues to push barriers by being the first female to achieve numerous certifications in the lubrication industry globally. She recently won Engineer of the year award 2024 from the Empowering Industry brand. Sanya sits on several international boards and has published 6 books to date. When not writing or managing the business, you can find her supporting projects to advocate for women in STEM.