❄️ Pour Point Temperature

Petrochemistry PN-EN ISO 3016

Overview

Pour point is the lowest temperature at which a petroleum product is still capable of flowing under standardized cooling conditions. Below this temperature, the network of paraffin crystals forms a gel that prevents liquid flow. Pour point is lower than cloud point — fuel first becomes cloudy (cloud point), and only at lower temperature stops flowing (pour point).

Pour point is a key parameter for lubricating oils, hydraulic and transformer oils, where low-temperature flow capability determines pumpability and lubrication under winter conditions. For engine and gear oils, pour point must be significantly lower than lowest operating temperature — otherwise oil will not reach lubricated surfaces during engine startup.

Standard PN-EN ISO 3016 describes manual and automatic methods. Sample is cooled in stages in baths of progressively lower temperature. Every 3°C test jar is removed and tilted — if sample does not move within 5 seconds, temperature 3°C higher is recorded as pour point. Standard describes separate procedure for residual fuels and heavy base oils (lower pour point).

Pour point is a mandatory parameter in lubricating oil specifications (SAE, ISO VG), transformer oils (PN-EN 60296), hydraulic and compressor oils. Oil producers use pour point depressants (PPD — Pour Point Depressants) — polymers that disrupt paraffin crystallization and lower pour point by 20–40°C.

Method principle

Sample is pre-heated to dissolve paraffin crystals, then cooled in series of controlled-temperature baths. Every 3°C test jar is removed from bath and tilted 90° for 5 seconds. If sample moves (flows), jar returns to bath and cooling continues. If sample does not move within 5 seconds, test is complete. Pour point = temperature of last movement + 3°C. In automatic apparatus, detection is based on optical monitoring of sample surface movement during tilting.

Applications

• Engine oil specification — SAE J300, winter pumpability limit
• Quality control of transformer oils (PN-EN 60296: pour point ≤ -40°C)
• Evaluation of hydraulic oils — pumpability at low temperatures
• Testing diesel fuel — pour point as informational parameter
• Quality control of crude oil — pipeline transport problems
• Evaluation of pour point depressant (PPD) effectiveness
• Testing gear and compressor lubricating oils
• Marine fuel specifications (ISO 8217)

Key parameters

Standard

Standard number

PN-EN ISO 3016:2019

Title (PL)

Przetwory naftowe i produkty pokrewne pochodzenia naturalnego lub syntetycznego — Oznaczanie temperatury płynięcia

Title (EN)

Petroleum and related products from natural or synthetic sources — Determination of pour point

Step-by-step procedure

1. Sample pre-heating

   Heat sample to temperature 12°C above expected pour point, not lower than 45°C. For samples with pour point > -33°C heat to 48°C in 48°C bath. Purpose is to dissolve paraffin crystals.

   ⏱ Time: 15–30 min • 🌡 Temperature: 45–48°C

2. Test jar filling

   Pour sample into clean, dry test jar to level mark (~45 mL). Insert thermometer and close with cork.

3. Cooling in first bath

   Place jar in bath at temperature dependent on expected pour point. For pour point > -33°C: 0°C bath as first.

   🌡 Temperature: 0°C

4. Flow test every 3°C

   At each 3°C sample temperature drop remove jar from bath. Hold horizontally and observe for 5 seconds whether sample moves. If it flows — return to bath.

   ⏱ Time: 5 s per test

5. Bath change

   When sample still flows in current bath — transfer to lower temperature bath (-18°C, -33°C, -51°C, -69°C). Continue tests every 3°C.

6. No flow determination

   When sample does not move within 5 seconds when jar is tilted — determination complete. Record temperature at which sample stopped.

7. Pour point calculation

   Pour point = stopping temperature + 3°C. For example: if sample did not flow at -21°C, pour point = -21 + 3 = -18°C. Result always multiple of 3.

8. Repeat determination

   Repeat test on new sample portion (again pre-heated). Two results should agree within repeatability limits (±3°C).

9. Reporting

   State pour point in °C (multiple of 3). State: PN-EN ISO 3016, sample identification, date. Clearly indicate whether result is "normal" or "lower" pour point.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Petroleum products — flammable, store away from ignition sources
• Baths with acetone + dry ice — flammable solvent at low temperature, dry ice causes frostbite
• Liquid nitrogen — risk of frostbite and asphyxiation in enclosed spaces, ventilation!
• Cryogenic gloves mandatory when handling low-temperature baths
• Safety glasses mandatory

Frequently asked questions