⛽ Gum content in gasoline
In short
Determination of existent gum content in gasoline by jet evaporation method with air or steam. The test is performed according to PN-EN ISO 6246:2017; Sample volume: 50 mL. The procedure comprises 11 steps (about 4 h 15 min–4 h 45 min in total); it is used for: Quality control of motor gasoline according to PN-EN 228 (max 5 mg/100 mL after washing), Testing oxidative stability of fuels during long-term storage, Quality control of aviation fuels (JET A-1) — steam method.
At a glance
- Standard: PN-EN ISO 6246:2017
- Category: Petrochemistry
- Procedure steps: 11
- Total time of stages: 4 h 15 min–4 h 45 min
- Sample volume: 50 mL
- Bath temperature: 160–240°C (depending on medium)
- Limit per PN-EN 228: max 5 mg/100 mL (washed gum)
Overview
Existent gum is the non-volatile residue after evaporation of a gasoline sample under controlled conditions. These are oxidation and polymerization products of unsaturated hydrocarbons (olefins) which under operating conditions can deposit on intake valves, intake manifolds, and combustion chambers, leading to deteriorated engine performance.
The PN-EN ISO 6246 method involves evaporating a measured volume of gasoline (50 mL) from a pre-weighed aluminum or glass beaker using a stream of hot air (for gasoline) or steam (for aviation fuels) at bath temperature of 160–240°C. After complete sample evaporation, the beaker is dried, cooled, and weighed. The mass difference represents the gum content expressed in mg/100 mL.
Quality requirements of PN-EN 228 for motor gasoline: gum content after washing max 5 mg/100 mL (washed gum). This value is very low and requires analytical precision. High gum values indicate fuel degradation (oxidation during storage), problems with oxidation inhibitors, or fuel contamination.
The standard also covers fuels with ethanol addition (up to 85% V/V) and ether oxygenates. Distinction is made between "washed" gum (washed gum — after additional heptane washing) and "unwashed" gum (unwashed gum). The reportable parameter is washed gum.
Method principle
A measured volume of fuel sample (50 mL) is placed in a pre-weighed aluminum beaker, then evaporated by a stream of hot air (flow 100 L/h per nozzle) in a heating bath with controlled temperature. Air is pre-heated in a heating coil, then directed onto the sample surface through a nozzle. After complete fuel evaporation, the beaker is dried in an oven (150°C, 30 min), cooled in a desiccator, and weighed on an analytical balance with 0.1 mg accuracy. For determination of "washed" gum, the residue is additionally rinsed with heptane, dried again, and weighed. The result is expressed in mg/100 mL.
Applications
- Quality control of motor gasoline according to PN-EN 228 (max 5 mg/100 mL after washing)
- Testing oxidative stability of fuels during long-term storage
- Quality control of aviation fuels (JET A-1) — steam method
- Evaluation of oxidation inhibitor effectiveness in fuels
- Monitoring fuel degradation in storage tanks
- Testing fuels with biocomponents (E5, E10, E85) — ethanol effect on gum
Key parameters
| Parameter | Value |
|---|---|
| Sample volume | 50 mL |
| Bath temperature | 160–240°C (depending on medium) |
| Limit per PN-EN 228 | max 5 mg/100 mL (washed gum) |
| Evaporation medium | Air (gasoline) / steam (aviation fuels) |
| Repeatability | r = 1.5 mg/100 mL (at 5 mg level) |
| Weighing accuracy | 0.1 mg |
Standard
- Standard number
- PN-EN ISO 6246:2017
- Title (PL)
- Przetwory naftowe — Zawartosc zywic w paliwach — Metoda odparowania strumieniem
- Title (EN)
- Petroleum products — Gum content of fuels — Jet evaporation method
Step-by-step procedure
-
Beaker preparation
Wash aluminum beakers with toluene, then acetone. Dry in oven (150°C, 30 min). Cool in desiccator. Weigh with 0.1 mg accuracy.
-
Bath heating
Turn on heating bath. Set temperature to required value (for gasoline: 160–240°C). Wait for stabilization.
-
Sample measurement
Pipette exactly 50 mL of gasoline sample into weighed beaker. Place beaker in bath socket.
-
Air stream activation
Set air flow to 100 ± 10 L/h per nozzle. Direct hot air stream onto sample surface. Begin evaporation.
-
Sample evaporation
Continue evaporation until complete gasoline evaporation (no visible liquid). Continue for 5 more minutes after evaporation.
-
Beaker drying
Remove beaker from bath. Place in oven (150°C, 30 min). Cool in desiccator to room temperature (30 min).
-
Weighing — unwashed gum
Weigh beaker with residue. Calculate unwashed gum content [mg/100 mL] = (m2 - m1) × 1000 / V.
-
Heptane washing
Add 25 mL heptane to beaker, gently rotate for 30 s, pour off heptane. Repeat 3 times. Heptane dissolves hydrocarbons, leaving gum.
-
Drying after washing
Place washed beaker in oven (150°C, 30 min). Cool in desiccator.
-
Weighing — washed gum
Weigh beaker. Calculate washed gum content [mg/100 mL]. This is the value reported per PN-EN 228.
-
Quality control
Perform blank test (50 mL heptane). Residue should not exceed 1 mg. Record duplicate results.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Jet evaporation bath for gum determination | Anton Paar PetroTest / Ayalytical (5 positions), Stanhope-Seta | 25,000–60,000 PLN |
| Aluminum beakers (tare cups) | Aluminum, d = 65 mm, pack of 100 pcs | 200–500 PLN / 100 pcs |
| Analytical balance (d = 0.1 mg) | Mettler Toledo XPR205, Sartorius Quintix 224 | 8,000–25,000 PLN |
| Laboratory oven | Binder FD 56, POL-EKO SLW 32 (150°C) | 4,000–12,000 PLN |
| Graduated pipette 50 mL | Class A pipette, DURAN borosilicate glass | 60–150 PLN |
| Desiccator | Glass desiccator with desiccant (silica gel) | 300–800 PLN |
| Compressor / air source | Oil-free compressor with flow regulator 100 L/h | 2,000–5,000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| n-Heptane (purity min. 99.5%) | 142-82-5 | For gum washing — determination of washed gum, high purity mandatory |
| Toluene | 108-88-3 | For cleaning beakers and apparatus, gum solvent |
| Acetone | 67-64-1 | For preliminary beaker cleaning, fast-drying |
Health and safety (OHS)
- Gasoline — extremely flammable, vapors forming explosive mixtures, work under fume hood in EX zone
- Heating bath — hot surface (up to 240°C), risk of burns, use heat-resistant gloves
- n-Heptane and toluene — flammable, toxic (toluene), work under fume hood
- Hydrocarbon vapors — use respiratory protection during prolonged exposure
- Safety glasses and laboratory coat mandatory
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 6246:2017 — “Petroleum products — Gum content of fuels — Jet evaporation method”.
How does this method work?
A measured volume of fuel sample (50 mL) is placed in a pre-weighed aluminum beaker, then evaporated by a stream of hot air (flow 100 L/h per nozzle) in a heating bath with controlled temperature. Air is pre-heated in a heating coil, then directed onto the sample surface through a nozzle.
What is the measuring range and accuracy?
Sample volume: 50 mL; Bath temperature: 160–240°C (depending on medium); Limit per PN-EN 228: max 5 mg/100 mL (washed gum); Evaporation medium: Air (gasoline) / steam (aviation fuels).
How long does the test take?
The times given for the individual stages add up to approximately 4 h 15 min–4 h 45 min. The procedure comprises 11 steps.
What equipment is required?
Jet evaporation bath for gum determination, Aluminum beakers (tare cups), Analytical balance (d = 0.1 mg), Laboratory oven, Graduated pipette 50 mL, Desiccator, Compressor / air source. Indicative cost of the core instrument (Jet evaporation bath for gum determination): 25,000–60,000 PLN.
Where is this test used?
Quality control of motor gasoline according to PN-EN 228 (max 5 mg/100 mL after washing); Testing oxidative stability of fuels during long-term storage; Quality control of aviation fuels (JET A-1) — steam method; Evaluation of oxidation inhibitor effectiveness in fuels; Monitoring fuel degradation in storage tanks; Testing fuels with biocomponents (E5, E10, E85) — ethanol effect on gum.
What safety precautions apply?
Gasoline — extremely flammable, vapors forming explosive mixtures, work under fume hood in EX zone; Heating bath — hot surface (up to 240°C), risk of burns, use heat-resistant gloves; n-Heptane and toluene — flammable, toxic (toluene), work under fume hood; Hydrocarbon vapors — use respiratory protection during prolonged exposure; Safety glasses and laboratory coat mandatory.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 6246.