Nylog® has earned a reputation as one of the most reliable sealants available for HVAC and refrigeration work. Getting the most out of that reliability starts with knowing which formulation is best for the job at hand. Refrigerant type, oil type, piping material and connection type all factor into which HVACR application sealant is most suitable.
The Science Behind Nylog’s Three Formulations
The differences between Nylog’s Blue and Red variants trace back to oil chemistry. Both are formulated to stay miscible with the lubricants already in the system. Since R-22 systems run mineral oil while modern HFC and A2L systems require POE, matching the sealant to the system’s existing oil ensures full compatibility from the start. That’s why selection between Blue and Red always starts with identifying what’s already in the system.
Nylog White, by contrast, is designed for applications outside the refrigerant line itself, such as o-rings, fittings and other non-refrigerant-contact components, so oil miscibility with system lubricants isn’t a factor in choosing it.
Nylog Blue®: The Universal HVAC Sealant for Modern Equipment
New A2L refrigerants, including R-32 and R-454B, continue to use POE oil, which means the shift away from R-410A doesn’t change the calculus for sealant selection on modern equipment. Nylog Blue® is a POE-based gasket and thread sealant that stays fully miscible with POE, PVE and PAG oils, making it the appropriate choice for R-410A, R-134a, HFO blends, CO₂ systems and the A2L refrigerants now entering the market.
On modern equipment, this is the sealant for HVACR applications that covers the widest range of jobs. It provides a flexible, non-hardening seal on flare fittings, threaded joints, o-rings and service valves while lubricating components during assembly. Like Nylog Red, small amounts entering the system remain compatible with system lubricants and won’t cause restrictions.
Common applications for Nylog Blue include:
- Flare fittings on R-410A, R-32, R-454B and HFO blend systems
- Threaded connections and service valves on modern residential and commercial equipment
- O-rings and gaskets in CO₂ refrigeration systems
- Any installation or repair work where POE, PVE or PAG oil is present
Nylog Red®: The Right Call for Older Refrigerant Systems
Nylog Red® is a mineral-oil-based gasket and thread sealant built for systems that run on mineral oil or alkylbenzene lubricants. If you’re working on R-22, R-12, ammonia or hydrocarbon systems, Nylog Red belongs on your flare fittings, threaded connections, schrader valves, o-rings and gaskets.
Because it’s formulated from mineral oil, it stays fluid and fully compatible with system lubricants. Any trace amount that enters the system won’t clog a TXV or restrict flow through a filter drier. It fills microscopic surface imperfections at sealing interfaces while lubricating threads to reduce the risk of galling or damage during assembly, which matters on older fittings that have seen multiple service cycles.
Common applications for Nylog Red include:
- Flare fittings on R-22 line sets and service connections
- Threaded fittings and service valves on older refrigeration equipment
- O-rings and gaskets in ammonia and hydrocarbon systems
- Schrader valve cores where a gas-tight seal is needed
Nylog White®: The Pipe Dope Sealant for Gas, Water and Mechanical Piping
Nylog White® operates in a different category entirely. While Nylog Red and Blue are oil-based refrigerant sealants, Nylog White is a PTFE-enhanced thread sealant designed for gas lines, water systems, hydronic piping, compressed air lines, steam connections and glycol systems. It’s the direct replacement for traditional pipe dope sealant and PTFE tape in mechanical applications.
The silicone and PTFE blend creates a durable, flexible seal that won’t dry out, harden or crack over time, which is a common failure with conventional pipe dope. It’s rated for extreme temperatures, safe for use on plastics, rubber and metal, and approved for food-area use, making it a practical choice across HVAC, plumbing and refrigeration work wherever refrigerant isn’t involved.
Common applications for Nylog White include:
- Natural gas and propane piping connections
- Hydronic heating system pipe threads and fittings
- Compressed air lines and fittings
- Water and glycol system connections
- Steam fittings and general mechanical assembly
Where Nylog Red, White and Blue All Agree
None of the Nylog sealants harden over time. That non-hardening property means connections stay serviceable — you won’t be fighting a joint that’s been locked in place by a cured sealant when you need to break it open two seasons later. All three products are also NSF registered and Kosher certified, covering incidental food contact applications including ice machines, beverage equipment and other food processing environments where this designation is required.
Nylog Blue | Nylog Red | Nylog White | |
Primary Use | Flare fittings, threaded connections, gaskets, o-rings in POE/PVE/PAG systems | Flare fittings, threaded connections, gaskets, o-rings in mineral oil/alkylbenzene systems | Pipe threads, fittings, gaskets in gas, water, air, steam and glycol systems |
NSF Registered/Food-Safe | Yes | Yes | Yes |
A2L Compatible | Yes | No | No |
Non-Hardening | Yes | Yes | Yes |
Know Your System, Choose Your Nylog
The right sealant for HVACR applications isn’t a one-size-fits-all decision, but it’s a straightforward one when you know what you’re working with. Whether it’s an older R-22 system, modern HFC equipment or a gas line, there’s a Nylog formulation built specifically for it. Match the formulation to the system, and Nylog handles the rest.