Yes, MO99 (also known as R-438A) is a direct, "no-oil-change" drop-in replacement for R-22. It is specifically engineered to replace R-22 in residential and commercial air conditioning, heat pumps, and refrigeration systems.
Of all the "no oil change" replacement refrigerants, Freon™ MO99™ offers the closest performance match to R-22. Freon™ MO99™ has compatibility with all traditional and new lubricants, including mineral oil (MO), polyolester (POE) oil, and alkylbenzene (AB) oil.
The best "drop-in" replacements for R22 are R407C for systems equipped with POE oil and R438A (Freon MO99) or R453A (RS-44B) for systems with existing mineral oil. Because true drop-in refrigerants don't exist, minor system retrofitting, such as changing valve cores, may be required.
No, you should never intentionally mix R-22 and MO99 (R-438A).
While marketing often claims certain products are "drop-in" replacements, there are no true, zero-effort "drop-in" replacements for R-22 that maintain identical performance without any modifications. Retrofitting requires careful, professional procedures, including changing oil types or replacing components to ensure system longevity and efficiency.
The most common, modern, and effective "drop-in" replacements for R-22 refrigerant in existing AC systems are R-438A (Freon MO99), R-453A (RS-44b), and R-407C. These alternatives are designed to work with existing mineral oil, often requiring no component changes, though a technician must perform the conversion.
R-22 refrigerant typically costs between $𝟗𝟎 and $𝟐𝟓𝟎 per pound. Because R-22 has been phased out, the supply is dwindling, which causes prices to continuously climb.
Yes, MO99 (formally known as R-438A) is widely used as a direct "drop-in" replacement for R-22 in existing air conditioning and refrigeration systems.
The best replacement for R-22 depends on your system's configuration. Because R-22 is fully phased out, the most common drop-in substitutes are R-438A (MO99), R-407C, and RS-44b (R-453A). These allow for system retrofits, though complete system replacement is often recommended for aging units.
A 30-pound cylinder of R-22 refrigerant is generally worth between $500 and $1,200 to purchase wholesale, and up to $2,400 to $4,500 if bought directly from a service company during a home repair.
Since Freon MO99 is the closest capacity match to R-22, compared with most of the other no-oil change refrigerants, it will reach the desired set point before other, lower-capacity refrigerants. With Freon MO99, residents are unlikely to know a different refrigerant is even being used.
No, you cannot put R407C on top of an existing R22 charge.
There are no refrigerants that can be safely or legally mixed directly into a system with R-22. Doing so can cause catastrophic compressor failure, severe pressure inconsistencies, and oil breakdown.
A2L refrigerants, the new refrigerants for 2026, will replace R-410A in new systems. A lot about A2L refrigerants is explained in their name: The “A” means low toxicity. The “2L” is a safety classification, indicating it is mildly flammable.
Freon™ MO99 has a temperature glide of 7–8 °F. This is similar to other R-22 replacement refrigerants. Because all zeotropic refrigerant blends have glide, the liquid and vapor have slightly different compositions. As a result, when charging a system, Freon™ MO99 should be removed from the cylinder as a liquid.
R438A (MO99)
R438A (Freon™/Isceon MO99) is a HFC blend, used as a replacement for R22 in domestic, industrial and commercial air-conditioning systems.
No, you should not mix Freon™ MO99 (R-438A) with R-22. While MO99 is designed as a retrofit for R-22 systems, mixing them can cause reduced system performance, inefficient operation, and potential long-term damage to the compressor.
The best "drop-in" replacements for R22 are R407C for systems equipped with POE oil and R438A (Freon MO99) or R453A (RS-44B) for systems with existing mineral oil. Because true drop-in refrigerants don't exist, minor system retrofitting, such as changing valve cores, may be required.
ALTERNATIVE REFRIGERANTS
R-458A TdX 20 by Bluon is a blend of five commercially used refrigerants. It delivers virtually identical capacity performance, significant energy savings, and extended equipment life. MO99 (R-438R) by Freon offers the closest performance match to R-22.
Freon™ MO99 is a non-ozone depleting HFC refrigerant designed to replace R-22 in existing DX residential and commercial AC and medium- and low-temperature refrigeration systems.
The best replacement for R-22 depends on your system's configuration. Because R-22 is fully phased out, the most common drop-in substitutes are R-438A (MO99), R-407C, and RS-44b (R-453A). These allow for system retrofits, though complete system replacement is often recommended for aging units.
The price of MO99 (also known as R-438A) refrigerant typically ranges from $𝟑𝟑𝟎 to $𝟒𝟓𝟎 for a 25-pound cylinder. If you are purchasing it per pound from a technician or local supplier, the cost generally ranges from $𝟏𝟎 to $𝟐𝟎 per pound.
A 30-pound cylinder of R-22 refrigerant is generally worth between $500 and $1,200 to purchase wholesale, and up to $2,400 to $4,500 if bought directly from a service company during a home repair.
Adding refrigerant to your central A/C system isn't something you should need to do regularly. In fact, a properly functioning system is designed to run efficiently without requiring frequent refills. On average, most central air conditioning systems need to have the refrigerant replaced ever two to five years.
R-22 is extremely expensive because it has been legally phased out. Driven by federal environmental regulations, skyrocketing supply chain costs, and contractor labor rates, prices range from $100 to $300+ per pound, meaning a standard refill can cost between $800 and $2,000+.