Qishanr QSL-PAG46 is a fully synthetic polyalkylene glycol (PAG) refrigeration compressor lubricant engineered around an ISO VG 46 base stock with a viscosity index of 192 and a pour point of -52°C. It is purpose-built for high-speed, small-displacement compressors in transport refrigeration, automotive air conditioning, and cold-chain applications where lighter viscosity reduces fluid friction at elevated RPM and extreme low-temperature fluidity is non-negotiable.
The -52°C pour point -- 7°C below that of QSL-PAG68 and 10-13°C below competing VG46 PAG oils -- makes QSL-PAG46 the cold-performance specialist of the Qishanr PAG family. Combined with VI 192, the oil maintains a flatter viscosity curve across the wide temperature swings that define transport refrigeration duty cycles: cold enough to flow at -30°C winter startup, stable enough to hold bearing film at +45°C condenser inlet temperatures on the highway. For a broader treatment of PAG chemistry and grade selection, see our PAG Refrigeration Oil Guide.
VG46 is not simply "VG68 but thinner." It is the correct specification for a specific compressor operating regime: high RPM, small displacement, and low to moderate bearing loads. In these applications, the heavier VG68 grade creates unnecessary fluid friction -- parasitic drag that converts directly to increased energy consumption and higher discharge temperatures with no compensating gain in bearing protection.
The decision framework is straightforward. If your compressor nameplate specifies VG46, deviating upward to VG68 will increase power draw by an estimated 3-5% in high-RPM reciprocating and scroll compressors, per the relationship between viscosity and churning loss in positive-displacement machines. The oil film in a compressor with bearing clearances of 15-25 microns -- typical for small scroll and automotive AC compressors -- is fully developed at VG46 viscosity; heavier oil simply increases shear stress in the bearing gap without improving separation of the running surfaces.
VG46 is the dominant specification for three application categories:
For medium-to-large semi-hermetic reciprocating and screw compressors in stationary commercial refrigeration, VG68 remains the correct grade. Qishanr offers QSL-PAG68 for those applications. The decision rule is simple: match the grade on the compressor nameplate. If the nameplate is unavailable, VG68 is the safe default for stationary commercial refrigeration; VG46 is the safe default for transport and automotive.
A cold storage facility operator in Harbin, northeast China, was running a blast freezer with a design evaporator temperature of -40°C. The facility's semi-hermetic reciprocating compressor was factory-charged with a standard VG46 PAG refrigeration oil rated at -39°C pour point. The arithmetic was simple and unforgiving: at -40°C evaporator temperature, an oil rated at -39°C pour point is 1°C below its own flow threshold -- the evaporator temperature minus the pour point gives -1°C, a negative margin. The oil was at or below its pour point at the coldest point in the evaporator circuit, where refrigerant velocity drops and oil tends to separate from the two-phase mixture.
The symptom was classic oil logging. The compressor sight glass showed dropping oil level during each pulldown cycle, requiring makeup oil additions every 60-90 operating days. Oil that should have circulated back to the sump was instead accumulating in the evaporator and suction accumulator as a cold, high-viscosity film that refused to move. During winter months, when Harbin ambient temperatures reached -30°C and the compressor room itself was below freezing, the problem worsened: cold-start oil pressure took an additional 8-12 seconds to stabilise, and bearing temperature excursions were recorded during the first five minutes of each startup.
The facility switched the compressor charge to QSL-PAG46, rated at -52°C pour point per GB/T 3535. The operating margin at the -40°C evaporator condition shifted from -1°C to a positive 12°C. Oil return stabilised within the first week of operation. The sight glass level held steady through repeated pulldown cycles, and cold-start oil pressure reached setpoint within 3 seconds even at -30°C compressor room ambient. Over the following twelve months, the facility eliminated two unscheduled oil changes and the associated eight hours of downtime per event that had previously been budgeted into their annual maintenance schedule.
This is not a testimonial -- it is field engineering arithmetic. Pour point is not a marketing number; it is the temperature below which oil ceases to flow under gravity in a standardised laboratory test. In a real evaporator, the effective pour point is the threshold below which oil film motion stops and oil inventory progressively accumulates in the low-pressure side of the system. A single-digit margin invites intermittent failure; a double-digit margin buys operational reliability. For cold chain operators running evaporators at -35°C and below, the -52°C pour point is the specification that decides whether the oil comes back or stays behind.
| Property | Value | Test Method |
|---|---|---|
| Oil Type | Polyalkylene Glycol (PAG) Synthetic | — |
| ISO Viscosity Grade | VG 46 | ISO 3448 |
| Kinematic Viscosity @ 40°C | 44.5 cSt | GB/T 265 |
| Kinematic Viscosity @ 100°C | 9.0 cSt | GB/T 265 |
| Density @ 20°C | 1,001 kg/m³ | GB/T 1884 |
| Viscosity Index | 192 | GB/T 1995 |
| Flash Point (COC) | 210°C | GB/T 3536 |
| Pour Point | -52°C | GB/T 3535 |
| Total Acid Number (fresh oil) | < 0.05 mg KOH/g | GB/T 7304 |
| Water Content (fresh oil) | < 80 ppm | GB/T 11133 |
| Copper Corrosion (3h @ 100°C) | 1a | GB/T 5096 |
| Available Capacities | 1 L / 5 L / 10 L / 20 L / 200 L | — |
A transport refrigeration unit assigned to a mixed-load delivery route in eastern China operates under a demanding thermal profile. The same truck handles frozen goods at -25°C setpoint on the morning run, then switches to chilled produce at +5°C for the afternoon return leg. The compressor sump temperature swings approximately 30°C across a single eight-hour shift -- from a cold-soaked startup at roughly 10°C sump temperature before the first pulldown, to a stabilised running temperature near 40°C after hours of continuous operation. This is not an edge case; it is the standard operating profile for multi-temperature transport refrigeration in cold chain logistics.
Viscosity index determines how much of that temperature swing translates into viscosity swing at the bearing. A typical POE VG46 oil with VI 130 loses approximately 40% of its kinematic viscosity between the cold and hot ends of this cycle. QSL-PAG46, with VI 192, loses approximately 22% over the same 30°C span -- a reduction of nearly half in the viscosity excursion. The practical consequence is bearing film thickness at the cold end of the cycle. At 10°C sump temperature, the POE VG46 is thick enough to delay oil pressure buildup and increase starter motor load; at 40°C, it has thinned to the point where film safety margin is reduced. QSL-PAG46 holds a narrower band at both ends -- thinner than the POE at cold start (easier cranking, faster pressure rise) and thicker than the POE at hot running (greater bearing separation).
Over 8,000 engine-hours -- roughly one year of continuous transport refrigeration service -- the cumulative effect of that flatter viscosity profile is measurable. The more stable oil film reduces boundary contact events in compressor bearings during the temperature transitions that occur multiple times per shift. Volumetric efficiency holds closer to design specification because the oil film in the cylinder bore and at the valve plate maintains consistent sealing characteristics rather than cycling between drag-heavy thick film at startup and leak-prone thin film at temperature. The energy arithmetic is straightforward: reduced viscous churning at the cold end plus maintained sealing at the hot end equals lower diesel consumption per refrigerated tonne-kilometre over the service year.
QSL-PAG46 is recommended for the following compressor types with VG46-specific application notes:
QSL-PAG46 is miscible with the following refrigerant families:
Not recommended for: Ammonia (R-717) systems, which require a fundamentally different lubricant chemistry. Hydrocarbon refrigerants (R-290, R-600a) generally perform better with mineral or alkylbenzene oils. For a complete compatibility matrix covering refrigerant-lubricant interactions, see our complete guide to refrigeration oil compatibility with HFC refrigerants.
PAG and POE are both synthetic refrigeration lubricants, but the chemistry drives materially different field performance. The table below compares QSL-PAG46 against a typical POE VG46 lubricant on the specifications that matter in service:
| Property | PAG46 (QSL-PAG46) | POE VG46 (Typical) |
|---|---|---|
| Viscosity Index | 192 | 100–130 |
| Pour Point | -52°C | -25°C to -45°C |
| CO2 (R-744) Compatibility | Excellent | Moderate |
| HFC/HFO Compatibility | Good | Excellent |
| Hygroscopicity | Very high | Moderate |
| Thermal Stability at High Discharge Temp | Excellent | Good |
| Typical Oil Change Interval | 8,000–15,000 hours | 6,000–10,000 hours |
The choice between PAG46 and POE VG46 depends on what the operating conditions demand. PAG46 wins decisively on pour point margin (-52°C vs a best-case -45°C for POE), viscosity stability across temperature swings (VI 192 vs 100-130), and CO2 compatibility -- making it the technically correct choice for transport refrigeration, cold chain, and transcritical CO2 systems. POE VG46 wins on lower hygroscopicity and broader OEM adoption for stationary HFC commercial refrigeration, where field service technicians routinely open containers under less-than-ideal humidity control.
For a broader analysis of lubricant chemistry selection, see our comparison of POE oil vs mineral oil for refrigeration systems.
PAG refrigeration oil is aggressively hygroscopic -- it absorbs atmospheric moisture at a rate significantly higher than POE or mineral oils. Water content above 200-300 ppm in service can hydrolyse the ester-based additive package and accelerate acid formation, eroding the extended oil life that PAG chemistry otherwise provides. Handling discipline is the single largest factor determining whether the oil delivers its design service interval or fails early.
If converting a system from mineral oil or POE to QSL-PAG46, a full system flush is mandatory. Residual mineral oil content must be verified below 1% by oil analysis before the system is returned to service. The flush procedure should use the new PAG oil as the flushing medium -- do not use solvent-based flushing agents unless specifically approved by the compressor manufacturer. Two to three flush-and-drain cycles are typically required to achieve residual contamination below the 1% threshold.
Material Safety Data Sheet (MSDS) documentation is provided with every shipment. For advance copy or batch-specific MSDS, contact the Qishanr technical team with the product lot number.
QSL-PAG46 has a pour point of -52°C, tested per GB/T 3535 -- the Chinese national standard equivalent to ASTM D97. This is 7°C below QSL-PAG68 (-45°C) and 10-13°C below most competing VG46 PAG oils, which typically range from -39°C to -45°C pour point. The -52°C rating provides a 12°C operating margin in blast freezer applications with -40°C evaporator temperatures, ensuring reliable oil return and eliminating the oil logging failures that occur when the compressor lubricant approaches its pour point inside the evaporator circuit.
The difference is viscosity grade. PAG 46 (ISO VG 46) has a kinematic viscosity of approximately 46 cSt at 40°C -- QSL-PAG46 measures 44.5 cSt per GB/T 265. PAG 68 (ISO VG 68) measures approximately 68 cSt at 40°C -- QSL-PAG68 measures 71.5 cSt. The practical distinction is application: VG46 is specified for high-speed, small-displacement compressors (transport refrigeration, automotive AC, small scroll units under 15 HP) where lighter viscosity reduces fluid friction and improves energy efficiency. VG68 is the general-purpose grade for medium-to-large semi-hermetic reciprocating and screw compressors in stationary commercial refrigeration. Using VG46 where VG68 is specified risks insufficient bearing film thickness; using VG68 where VG46 is specified increases energy consumption by 3-5%. Always match the viscosity grade to the compressor nameplate specification.
Yes. QSL-PAG46 is compatible with CO2 (R-744) refrigeration systems across all three major architectures: subcritical cascade, transcritical booster, and secondary-loop systems. PAG chemistry is the preferred lubricant for CO2 applications because it maintains controlled partial solubility in supercritical CO2 at pressures exceeding 100 bar -- a condition under which POE oils suffer excessive viscosity dilution. The VI 192 rating of QSL-PAG46 ensures stable lubricant film thickness from the low-temperature side of the cycle (-35°C in the evaporator) to the high-temperature side (up to 140°C at the discharge of a transcritical compressor).
VG46 refrigeration oil is specified for high-speed, small-displacement compressors where lighter viscosity reduces fluid friction and improves cold-start performance. The primary application categories are: transport refrigeration compressors (Carrier Transicold, Thermo King units operating at 2,000-3,500 RPM), automotive air conditioning compressors (R-134a and R-1234yf systems, virtually all OEM factory-fill specifications), small scroll compressors under 15 HP, and cold storage/blast freezer compressors where an ultra-low pour point is required for reliable oil return at evaporator temperatures below -35°C. Medium-to-large semi-hermetic reciprocating and screw compressors in stationary commercial refrigeration typically specify VG68.
No. Do not mix QSL-PAG46 with POE (polyol ester) oil. PAG and POE are chemically distinct synthetic lubricant families and are not mutually miscible in all proportions. The additive packages are formulated for their respective base chemistries, and cross-contamination can cause additive dropout, impaired refrigerant miscibility, and unpredictable viscosity behaviour. If converting a system from POE to PAG, perform a full flush with the new PAG oil as the flushing medium and verify residual POE content below 1% by oil analysis before returning the system to service. The same prohibition applies to mixing PAG with mineral oil or alkylbenzene lubricants.
Material Safety Data Sheet (MSDS) documentation for QSL-PAG46 is provided with every shipment in both Chinese and English language versions. For a digital copy, the technical data sheet and MSDS are available for download on the product page or can be requested directly from the Qishanr technical support team by providing the product lot number. Batch-specific MSDS documentation ensures that the safety data matches the exact formulation of the oil in your shipment -- important for procurement teams managing regulatory compliance across multiple jurisdictions.
