Automotive A/C Refrigerants

Direct Answer

Automotive air conditioning refrigerants are standardized under SAE J639, SAE J2842, and EPA regulations into R-12 (CFC-12 legacy), R-134a (HFC-134a standard since 1994), and R-1234yf (HFO ultra-low GWP standard on modern vehicles), each featuring unique quick-connect service port dimensions and dedicated synthetic compressor oils (PAG vs POE).

Source: SAE J639 / SAE J2842 / EPA Clean Air Act Section 609 / ASHRAE Standard 34 · Last reviewed Aug 28, 2026

Specs

Governing Standards	SAE J639 / SAE J2842 / ASHRAE 34 (Refrigerant Safety) / EPA SNAP Program
R-12 (Dichlorodifluoromethane)	Global Warming Potential (GWP): 10,900 \| Ozone Depletion Potential (ODP): 1.0 \| 7/16" threaded flare ports \| Mineral oil
R-134a (1,1,1,2-Tetrafluoroethane)	GWP: 1,430 \| ODP: 0.0 \| High-side 16 mm / Low-side 13 mm quick-connect ports \| PAG 46/100/150 oil
R-1234yf (2,3,3,3-Tetrafluoropropene)	GWP: < 1.0 \| ODP: 0.0 \| High-side 17 mm / Low-side 14 mm left-hand keyed ports \| PAG/POE specialized oils
R-744 (Carbon Dioxide / CO2)	GWP: 1.0 \| Transcritical system operating at ultra-high pressures up to 130 bar (1,885 psi) \| Mercedes S-Class option
Standard Low-Side Operating Pressure	25 to 45 psi (1.7 to 3.1 bar) at 21°C–32°C (70°F–90°F) ambient
Standard High-Side Operating Pressure	150 to 250 psi (10.3 to 17.2 bar) depending on ambient condenser airflow
Oil Compatibility Rule	Never use mineral oil with R-134a/R-1234yf; PAG oil is strictly hygroscopic (absorbs atmospheric moisture rapidly)

Automotive A/C Refrigerant Technical Specification & Port Matrix

Refrigerant Code	Chemical Classification	Global Warming Potential (GWP 100-yr)	Low-Side Port Fitting	High-Side Port Fitting	Standard Compressor Lubricant
R-12 (Freon)	CFC (Chlorofluorocarbon)	10,900	7/16"-20 Threaded Flare	3/8"-24 Threaded Flare	Mineral Oil (525 Viscosity)
R-134a (Standard)	HFC (Hydrofluorocarbon)	1,430	13 mm Quick-Connect	16 mm Quick-Connect	PAG 46 / PAG 100 / PAG 150
R-1234yf (Modern)	HFO (Hydrofluoroolefin)	< 1.0 (0.3)	14 mm Quick-Connect	17 mm Quick-Connect	Double-End-Capped PAG / POE
R-744 (CO₂)	Natural Gas	1.0	Ultra-High Pressure Special	Ultra-High Pressure Special	Synthetic POE / PAG Extreme Pressure

Why R-1234yf Uses Unique 14mm/17mm Mechanical Port Dimensions

To prevent catastrophic refrigerant cross-contamination:

SAE J639 Port Keying: The service couplers on R-1234yf recovery machines are physically 1 mm larger (14 mm low / 17 mm high) with specialized left-hand lock keys. This mechanically prevents a technician from accidentally connecting an R-134a manifold hose to an R-1234yf vehicle.
Mild Flammability (ASHRAE A2L): R-1234yf is classified as mildly flammable (A2L), requiring spark-free recovery machines and brushless evaporator blower fan motors.