By Qishanr Technical Team · Published 20 September 2026
Repeat order · QSL-PAG46 · Truck fleet AC compressors and transport refrigeration
QSL-PAG46 is a fully synthetic polyalkylene glycol (PAG) refrigeration compressor oil in the ISO VG 46 grade. It is built for the high-speed, small-displacement compressors a fleet runs under the bonnet and inside its transport refrigeration units.
| Customer | A fleet maintenance company running trucks and five service branches (not named) |
| Application | AC compressors in the fleet, serviced across five branches |
| Product | Qishanr QSL-PAG46, ISO VG 46 PAG — 44.5 cSt at 40 °C |
| Timeframe | First order two years ago; repeat order placed for the current season |
| Repeat order | 500 cans of 3.78 L (1 gallon) |
| Service result | Over two years with no sludge, no viscosity drift and no compressor comebacks |
| Supply result | Batch quality consistent with the first shipment; leak-free cans after sea freight; promised lead time kept |
This customer first ordered the oil two years ago, and was asked how it had held up across the fleet. Their reply is quoted in full:
First ordered the 3.78 L cans two years ago for our truck fleet's AC compressors. That oil has held up in systems for over 2 years with no signs of breakdown — no sludge, no viscosity drift, no compressor comebacks. When we needed to stock up for this season across our 5 service branches, reordering from the same supplier was an easy decision. We just received our repeat order: 500 cans of 3.78 L (1 gallon). Batch quality is consistent with the first shipment, packaging arrived leak-free despite sea freight, and the supplier kept the promised lead time with regular updates. Same spec, same performance, bigger order. We'll keep buying from this supplier and recommend them to any fleet or maintenance company looking for dependable refrigeration oil.
Compressors in mobile duty are small and fast. A belt-driven AC compressor turns at about 800 RPM at idle and can pass 6,000 RPM on the highway. A transport refrigeration unit typically holds 2,000–3,500 RPM at cruise.
Bearing clearances in that class of machine run 15–25 microns. The oil film therefore forms at a moderate viscosity rather than a heavy one.
ISO VG 46 is the grade built for that regime. Viscosity grade is a classification within the ISO 3448 system, and VG46 is the dominant specification for both transport refrigeration and automotive AC compressors. The same machine on a heavier VG68 adds fluid friction at high shaft speed without improving separation of the running surfaces.
Two measured numbers place the oil in that grade: a kinematic viscosity of 44.5 cSt at 40 °C and 9.0 cSt at 100 °C. Kinematic viscosity in this class is determined under ASTM D445, the method that measures a lubricant's resistance to flow at a controlled temperature.
The cold end of the envelope matters just as much to a fleet. QSL-PAG46 has a pour point of −52 °C — 7 °C below the VG68 grade in the same family, and 10–13 °C below typical VG46 PAG oils.
A pour point is the temperature below which an oil stops flowing under gravity in a standardised test. For a fleet it answers one practical question: does oil reach the bearings on a winter-morning first start?
Two years is long enough for the slow mechanisms to appear. The two signals this customer named are the two a workshop can read without a laboratory.
Sludge is the insoluble deposit that forms when oxidation products and moisture collect in a circuit instead of circulating. In a PAG system, moisture is the usual way in, because these oils absorb water from the air.
A can left open on a branch shelf, a damp charging hose, or a filter drier kept past its change date all feed the same reaction.
Viscosity drift is the second signal. It describes an oil whose measured viscosity has moved away from its original value — thinned by refrigerant dilution and shear, or thickened by oxidation and moisture.
Viscosity index states how strongly viscosity changes across a temperature span. QSL-PAG46 is rated at VI 192, calculated from the 40 °C and 100 °C values per ASTM D2270.
Both signals are read the same way at branch level. Appearance at each service, acid value and moisture where the branch samples, and a top-up record that stays flat are enough to show a trend forming before it turns into a compressor repair.
The two are linked. An oil that is absorbing little moisture and oxidising slowly keeps both its colour and its viscosity — which is what a two-year report of no sludge and no drift describes.
A first order tests whether one can matches its data sheet. A repeat order of 500 cans tests four things at once: batch reproducibility, pack sealing, transit protection and lead-time discipline.
Batch consistency comes first. The customer reports the second shipment matching the first. That is precisely what a five-branch operation depends on: one grade, one pack, one behaviour, so a branch cannot fit the wrong oil by accident and no site is surprised by a fresh delivery.
Sealing comes second. Cans cross the sea in cartons, stacked and shifting for weeks. The customer reports the shipment arriving leak-free. For a PAG that matters more than for most oils, because absorbed moisture goes to work whether the can is in service or in store.
Lead time comes third. Fleet maintenance is seasonal: stock has to be on the shelf before the load arrives, not after. The customer notes the promised lead time was kept, with regular updates through the order.
The refrigerant half of the picture comes fourth. Mobile AC refrigerants are regulated, and the EPA's SNAP program publishes which substitutes are acceptable in that application.
As fleets move from R134a to R1234yf, one oil has to serve both. QSL-PAG46 is specified for HFC, HFO and CO₂ refrigerant systems, so a single branch line item covers a mixed fleet.
A first order can only test the first two of those. A 500-can repeat tests all four, and the customer's answer covers each one.
The values below are the QSL-PAG46 reference data used across our PAG refrigeration oil guides, together with the test methods behind each one.
| Parameter | Value | Method |
|---|---|---|
| Oil type / grade | Synthetic polyalkylene glycol (PAG), ISO VG 46 | ISO 3448 |
| Kinematic viscosity @ 40 °C | 44.5 cSt | GB/T 265 |
| Kinematic viscosity @ 100 °C | 9.0 cSt | GB/T 265 |
| Viscosity index | 192 | GB/T 1995 |
| Density @ 20 °C | 1,001 kg/m³ | GB/T 1884 |
| Flash point (COC) | 210 °C | GB/T 3536 |
| Pour point | −52 °C | GB/T 3535 |
| Copper corrosion, 3 h @ 100 °C | 1a | GB/T 5096 |
| Pack supplied on this order | 500 cans of 3.78 L (1 gallon) | Customer order |
The chart below shows the property a fleet feels every shift and a table cannot show: how much of its viscosity the oil keeps as the system warms from a cold-soak start to steady running.
Fig. 1 — Viscosity retained across a 30 °C swing in a transport refrigeration duty cycle, both curves referenced to the cold end at 10 °C. QSL-PAG46 (VI 192) retains roughly 78% of its cold-end viscosity at 40 °C, against about 60% for a typical VI 130 POE VG46.
A: It is an ISO VG 46 PAG made for high-speed, small-displacement compressors, which is the class used in transport refrigeration units and vehicle AC. Confirm the grade against the compressor nameplate or the vehicle service specification before filling, then set the pack size and quantity per branch. If the nameplate asks for VG68, use the VG68 grade instead.
A: VG46 suits fast, small machines, where a heavier oil increases fluid friction without improving bearing separation. VG68 remains the correct grade for slower, larger semi-hermetic reciprocating and screw compressors in stationary commercial refrigeration. A fleet that standardises workshops on the nameplate grade avoids both mistakes at once.
A: Compare the delivered batch against the first shipment: request the certificate of analysis for the batch, keep a retained sample of the earlier fill, and inspect appearance and pack sealing on arrival. For a PAG, confirm the cans are sealed and the store is dry, because the oil takes up moisture from the air.
A: Pack size is confirmed at quotation, so a fleet can standardise on the pack that works at branch level. The customer in this case ran their reorder as 500 cans of 3.78 L (1 gallon), sized for workshop top-ups across five branches, with larger packs available for bulk filling.
A: Send the grade previously supplied, the pack size, the quantity per branch, the refrigerant and compressor type, the destination, and any documents your inspection requires. With those details the quotation confirms pack, batch, lead time and shipping terms before the order is placed.
Stocking a fleet for the season? Send the compressor type, refrigerant, pack size and quantity per branch — we confirm batch, lead time and shipping terms before you order. Request a QSL-PAG46 Quotation
