Car A/C systems run on two fluids: a refrigerant and a compressor oil. The refrigerant handles the actual cooling; the oil keeps the compressor lubricated. This is where your PAG oils come in.
PAG 46 and PAG 100 are both polyalkylene glycol (PAG) synthetic lubricants, but they are not interchangeable. PAG 100 is the thicker between the two.
The number in each oil’s name refers to its approximate kinematic viscosity at 40°C, measured in centistokes (cSt). PAG 46 runs at roughly 41–51 cSt. PAG 100 runs at roughly 95–100 cSt.
Thicker oil means more drag on the compressor. That is why most modern passenger vehicles use PAG 46. Lower viscosity reduces engine load, which supports better fuel economy.
PAG 100, by contrast, is specified for applications where that extra film thickness matters.
PAG 100 shows up in older R134a systems and in vehicles from manufacturers like Subaru and certain older GM compressors. The 1994 Jeep Cherokee is one commonly cited example. Outside of automotive A/C, PAG 100 also sees use as an industrial gear oil in high-load gearboxes, worm gears, and circulating systems in industries like steel, paper, and cement. Its manufacturer equivalents include SP-15 and SP-20.
PAG 46 Oils for Car A/C Systems
PAG 46 is the most widely specified compressor oil for modern automotive A/C systems, and the options below cover the main variants you’ll encounter: standard R-134a, R-1234yf-specific, and formulations with UV dye built in for leak detection.
Supercool 27262D PAG 46 with UV Dye (R-1234yf)
TSI Supercool 27262D 1234yf PAG 46 Viscosity with UV Dye
Supercool 27262D PAG 46 is an R-1234yf-specific PAG 46 from Supercool, with UV dye built in.
This is formulated specifically for R-1234yf systems, not a universal PAG 46. It contains moisture inhibitors, anti-wear agents, and a conditioner package to protect seals and internal compressor components.
Supercool 27262-12CP PAG 46H (R-1234yf)
TSI Supercool 27262 1234yf PAG 46H Compressor Fluid
Supercool 27262-12CP PAG 46H is an R-1234yf-specific aftermarket PAG 46 from TSI Supercool.
Unlike the previous product, this one doesn’t contain UV dye. This oil’s additive package, which includes conditioners, inhibitors, and anti-wear agents, is built around the requirement for R-1234yf systems.
HCPRO HCP46UV8 PAG 46 with UV Dye (R-134a)
HCPRO HCP46UV8 PAG 46 Viscosity Plus UV Dye Lubricant
This is an R-134a aftermarket PAG 46 from HCPRO, formulated to meet OEM specifications, with UV dye integrated for leak detection.
HCPRO includes the standard additive bases: conditioners, inhibitors, anti-wear agents, and corrosion protection. Nothing unusual in the formulation, which is appropriate for a general-purpose PAG 46.
This suits owners of R-134a vehicles where PAG 46 is the specified grade, who want a straightforward aftermarket option with leak detection included.
PAG 10 Compressor Oils
PAG 100 is the less common of the two grades, but some compressor designs specifically require the thicker viscosity. The options below cover R-134a and R-1234yf applications, with and without UV dye.
Supercool P100-8D PAG 100 with UV Dye (R-134a)
TSI Supercool P100-8D PAG Oil 100
TSI Supercool claims that this product meets OEM performance specifications, with the usual UV dye included for leak detection.
PAG 100 sees less use than PAG 46 in modern systems, but it remains the specified grade for certain compressor designs and manufacturers. The thicker film provides more wear protection in piston-style compressors.
This product contains anti-oxidant additives to prevent sludge buildup. The friction modifiers work alongside the base viscosity to reduce wear at the compressor’s contact surfaces.
Supercool 38589 PAG 100 (R-1234yf)
TSI Supercool 38589 1234yf PAG 100 Viscosity
PAG 100 is a less common viscosity grade for 1234yf systems, but it exists for certain compressor designs.
Most R-1234yf vehicles call for PAG 46, so if you are reaching for this, your compressor tag or service manual should explicitly state PAG 100. Do not substitute this for PAG 46 based on availability. The thicker film changes the lubrication dynamics the compressor was engineered around. This is different from the previous product with its “H” designation, which indicates a high-moisture-resistance formulation.
Johnsen’s 6816UV-6 PAG 100 with UV Dye (R-134a)
Johnsen’s 6816UV-6 ISO 100 Premium PAG Lubricant with UV Dye
What makes this product unique is the SAE-approved UV dye. Not all UV dyes meet SAE standards, and using a non-approved dye can leave residue that interferes with future diagnostics.
If your system calls for PAG 100, this is yet another straightforward aftermarket option.
Do NOT Mix PAG 46 and PAG 100
Mixing PAG 46 and PAG 100 creates an unpredictable viscosity blend that your compressor was not designed for. If you are switching grades, flush the system first. The compressor needs to receive exactly the lubrication it was engineered around.
Using the wrong viscosity altogether carries real risk. A compressor starved of proper lubrication or flooded with oil that is too thick can seize. This can lead to a catastrophic failure.
“46” and “100” is only half the equation. The refrigerant in your system determines which chemical formulation of PAG oil is acceptable. First, a quick look back into history.
R134a became the automotive standard in 1994, replacing the ozone-depleting R-12. It does not harm the ozone layer, but its high Global Warming Potential (GWP) has pushed regulators and manufacturers toward phasing it out.
This newer refrigerant is now standard in vehicles like the 2018–2019 Chevrolet Equinox.
R-1234yf replaced R134a. It carries a much lower GWP and is now standard in newer vehicles, including the 2018–2019 Chevrolet Equinox.
R134a systems are compatible with standard PAG 46, PAG 100, or PAG 150. These oils offer the moisture resistance and anti-wear protection the compressor needs, and they are chemically stable alongside R134a.
R-1234yf systems require specific chemical additives. Because of the refrigerant’s reactive chemistry, even a PAG 46 oil labeled for R134a is not automatically safe to use. You need an oil specifically formulated and labeled to be compatible with R-1234yf. The key viscosity grade may look the same on the bottle, but the additive chemistry is different.
R-1234yf-compatible PAG oil can generally be used in an R134a system without issue. The reverse is not true. Standard R134a PAG oil should never go into an R-1234yf system.
How to Confirm if You Need PAG 46 or 100
Check the under-hood sticker first. Most vehicles manufactured after the mid-2000s list the refrigerant type and the required oil viscosity directly on a label near the A/C service ports.
For example, Ford lists the required refrigerants for its vehicles.
If the sticker is missing or unreadable, the compressor manufacturer’s tag or your owner’s manual will have the specification.
Manufacturers often use proprietary codes rather than plain numbers. PAG 46 typically appears as ND-8 or Atmos GU10. PAG 100 shows up as SP-15, SP-20, or SP-22 on Sanden compressors. If neither label is available, your owner’s manual or factory service manual will have the official specification.
As a general rule, vehicles running R-1234yf, common from around 2018 onward, typically require a specialized PAG 46. R-134a systems vary more widely; PAG 46, 100, or 150 are all possible depending on the compressor design.
One additional check: if you are installing a replacement compressor, verify the oil type and quantity that came pre-filled in the new unit before installation. That amount needs to be accounted for against your system’s total capacity.
Closing Note
PAG oil is highly hygroscopic, meaning it absorbs moisture from the air the moment the bottle is opened. That moisture reacts over time to form acid inside the system, corroding components from the inside out. Never use oil from a container that has been left open or stored unsealed.
Looking ahead, PAG oil is not the only option on the market. Electric and hybrid vehicles increasingly require POE (polyol ester) oil, which is non-conductive and safe for use around high-voltage electric compressors. PAG oil is not suitable for these systems.
