If you are considering installing gas equipment on your car or are already using HBO, then you have probably encountered the terms LPG and propane. Many drivers mistakenly believe that these are the same thing. In fact, there is a difference - and it affects engine performance, fuel consumption and even safety. In this article we will figure out what it is LPG, what it consists of, why it cannot be called pure propane and how to choose the right gas for your car.

Spoiler: LPG is not just propane, but a mixture of hydrocarbons, where propane plays a key, but not the only role. The octane number, pressure in the cylinder and even the life of engine parts depend on the composition. If you refuel "by eye", without knowing what is pouring into the cylinder, you risk encountering problems - from increased consumption to gearbox failure. Next, we’ll tell you how to avoid mistakes and what you need to know about gas for LPG.

What is LPG and why is it confused with propane?

LPG (liquefied petroleum gas) is a general term for mixtures of light hydrocarbons that become liquid at room temperature and low pressure. In the automotive industry, LPG usually means propane-butane mixture, but its composition may vary. Pure propane (C₃H₈) is just one of the components, and in reality you will rarely find 100% propane at gas stations.

Main reasons for confusion:

  • 🔹 Marketing: at many gas stations they simply write “propane”, although they sell a mixture.
  • 🔹 Technical documentation: in instructions for gas equipment, “propane” is often mentioned, meaning LPG.
  • 🔹 Habit: Drivers are accustomed to calling any automobile gas “propane.”

In practice, a mixture is poured into the cylinder, where propane can be from 40% up to 90%, and the rest is butane (C₄H₁₀) and impurities (methane, ethane, pentane). The ratio depends on the season, region and even supplier. For example, in winter the proportion of propane is increased so that the gas does not freeze in the cylinder, and in summer more butane is added to save money.

📊 What gas do you fill in the LPG?
Propane-butane (LPG)
Pure propane
Methane
I don’t know what they pour at my gas station

LPG composition: propane vs butane and other components

To understand why LPG is not equal to propane, let’s look at its typical composition. In Russia and the CIS countries, automobile gas is regulated GOST 27578-87 and GOST R 52087-2003. According to these standards, LPG may include:

Component Chemical formula Share in the mixture, % Impact on HBO
Propane C₃H₈ 40–90 High octane number (110+), good volatility at low temperatures
Bhutan C₄H₁₀ 10–60 Cheaper than propane, but evaporates worse in cold weather (may cause starting problems)
Methane CH₄ up to 5 Increases detonation resistance, but requires high pressure (rarely found in LPG)
Ethan C₂H₆ up to 2 Has virtually no effect on engine operation, but reduces the calorific value of the mixture
Pentane and heavy hydrocarbons C₅H₁₂+ up to 1 They can clog filters and settle in the mains (they should not be present in high-quality LPG)

Critical difference: propane boils at −42°C, and butane at −0.5°C. This means that in winter, a mixture with a high butane content may not evaporate in the cylinder, which is why the engine will not start. This is why the LPG composition at gas filling stations is seasonally adjusted, and in the northern regions there is always more propane in the mixture.

Another nuance: the octane number of propane is 110–115, and butane - 90–95. The more butane in the mixture, the lower its anti-knock properties. This is important for modern turbocharged engines, where low octane can lead to detonation and piston damage.

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Before winter, check the composition of the gas at your gas filling station - if the share of butane exceeds 40%, you should look for another gas station or add an anti-gel additive for LPG to the cylinder.

How to determine what is in a cylinder: propane or LPG

It is impossible to distinguish pure propane from a propane-butane mixture by eye. However, there are several ways to check the composition:

  1. Refueling receipt: Some gas stations indicate the percentage of propane and butane. For example, "Propane 60% / Butane 40%".
  2. Cylinder color: in Russia they use LPG red cylinders, and for methane - black or red with yellow stripe. But this is not a guarantee of composition!
  3. Smell: pure propane has practically no smell, and an odorant is added to the LPG (usually ethyl mercaptan) to detect leaks. If the gas has a strong "gassy" smell, it is a mixture.
  4. Cylinder pressure: propane creates a pressure of ~16 atm at +20°C, and butane - ~2 atm. If you have a pressure gauge, you can roughly estimate the composition.
  5. Laboratory analysis: The most accurate method is to take a gas sample to a specialized laboratory (for example, Rostest or SGS-groups).

If you refuel at an unfamiliar gas station, pay attention to the price: pure propane is usually more expensive than the mixture by 10–20%. You can also ask the operator what kind of gas they sell - some gas stations work directly with gas processing plants and can provide a quality certificate.

What happens if you fill in methane instead of LPG?

Methane (LPG) and LPG are different types of gas, incompatible in terms of equipment. If you pour methane into an LPG cylinder, the following will happen:

1. The pressure in the cylinder will increase to 200–250 atm (for LPG - up to 16 atm), which will lead to rupture.

2. The gearbox and lines are not designed for such pressure - they will burst.

3. HBO injectors will not be able to dose methane correctly due to a different density.

Never fill methane into a system intended for LPG, and vice versa!

The influence of LPG composition on the operation of gas equipment and the engine

Not only engine starting in winter depends on what gas you fill, but also:

  • 🔧 Resource of the reducer-evaporator: butane evaporates worse, which causes the gearbox to work under increased load and may fail.
  • ⚡ Engine power: propane gives on 3–5% more power due to better volatility and octane number.
  • 💰 Fuel consumption: butane is cheaper, but its calorific value is lower - gas consumption increases by 5–10%.
  • 🔥 Knock resistance: High butane content can cause detonation in high compression engines.

For example, if your LPG is configured for propane, and you filled the mixture with 60% butane, may occur:

  • 🔴 Problems with cold starting (gas does not evaporate, engine stalls).
  • 🔴 Power loss at high speeds (insufficient gas supply).
  • 🔴Increasing consumption for 10–15%.

Solution: modern gas equipment systems (for example, Lovato, BRC or Stag) have temperature and pressure sensors that automatically adjust the gas supply. But if you have budget equipment, it is better to refuel with propane with a minimum butane content.

Check the composition of the gas at the gas filling station (the share of butane is no more than 40%)

Fill the tank 80% (leaving room for gas to expand)

Warm up the gearbox before starting (turn on the ignition for 10–15 seconds)

Use winter lubricant on gas valves

Check the tightness of the system (for example, with a soap solution)

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Myths about LPG: what is true and what is not

There are many myths surrounding automobile gas. Let's look at the most common ones:

Myth 1: "Pure propane is better for the engine than LPG"

✅ Partly true. Propane does have more stable characteristics, but modern engines also work well on a high-quality propane-butane mixture. The main thing is that there is no more butane 40–50%.

Myth 2: “Butane ruins the engine”

❌ Not true. Butane does not harm the engine if the LPG system is configured correctly. Problems arise only when the ratio of components is incorrect or the quality of the gas is low (for example, with sulfur impurities).

Myth 3: “In winter you need to drain the gas from the cylinder”

❌ Dangerous Misconception. Draining gas is not only pointless, but also dangerous! It is enough to refuel with high-quality LPG with a high propane content (at least 60%) and do not leave the container empty (minimum 10% gas must remain for pressure).

Myth 4: “LPG is more explosive than gasoline”

✅ True, but with reservations. Gas is indeed more easily flammable, but modern gas cylinders are designed for pressures up to 30 atm and are equipped with safety valves. If installed correctly, the risk of explosion is minimal.

Myth 5: “The engine is quieter on gas”

✅ True. The octane number of LPG is higher than that of gasoline, so detonation is reduced and the engine runs smoother. However, this depends on the settings of the HBO.

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High-quality LPG with a predominance of propane (60% and above) has characteristics close to pure propane and is suitable for most engines. The main thing is to avoid cheap mixtures with a high content of butane and heavy hydrocarbons.

How to choose the right gas for LPG: expert advice

To avoid problems with engine and gas equipment operation, follow these recommendations:

  1. Choose proven gas stations: refuel at network stations (Gazpromneft, Lukoil, Rosneft), where the gas undergoes quality control. Avoid "left" gas stations with suspiciously low prices.
  2. Follow the seasonal lineup:
    • 🔹 Winter: propane share - no less 60%.
    • 🔹 Summer: acceptable 40–50% propane, but no less.
  • Check the pressure in the cylinder: if after filling the pressure at +20°C is lower 5–6 atm, there is too much butane in the mixture.
  • Use additives: for winter use, you can add special additives to the cylinder (for example, Gas Treatment from Liqui Moly), which improve the volatility of butane.
  • Adjust gas equipment to the gas composition: if you refuel with a mixture with a high butane content, ask your technician to adjust the gas supply maps to the ECU.

    • If you often travel long distances, carry a portable gas analyzer (for example, Gas Detector from Elitech). It will help you quickly check the gas composition at an unfamiliar gas station.

    💡

    After filling with new gas, drive 5–10 km and evaluate the engine performance. If there are dips, detonation, or consumption increases, there is most likely too much butane in the mixture. In this case, it is better to drain the gas and refuel at another gas station.

    What to do if you have filled in with low-quality LPG

    If after refueling you notice problems (poor starting, jerking, check engine), follow the algorithm:

    1. Don't panic: filling up with bad gas once is not critical for the engine, but driving it for a long time is not worth it.
    2. Try diluting the gas: fill propane on top of low-quality LPG from another gas station (if there is space in the cylinder).
    3. Drain the gas:
      • 🔹 Turn off the gas supply (close the multivalve).
      • 🔹 Connect the hose to the cylinder drain fitting and release the gas in a well-ventilated place (away from open flames!).
      • 🔹 Never discharge gas down a drain or onto the ground. - it is dangerous and illegal.
  • Flush the system: if the gas contained heavy impurities (for example, oils), it may be necessary to replace the LPG filters.
  • Check ECU settings: After changing gas, fuel maps may need to be adjusted.

    • ⚠️ Attention: If after refueling there is a strong smell of sulfur or gas in the cabin, stop immediately, close the multi-valve and ventilate the car. This may indicate a leak or the presence of hazardous contaminants (such as hydrogen sulfide).

    If the problem persists, have a gas sample analyzed and contact your supplier with the results - as required by law (Federal Law No. 261) you have the right to demand compensation for low-quality fuel.

    FAQ: Frequently asked questions about LPG and propane

    Is it possible to fill pure propane into an LPG cylinder?

    Yes, pure propane is fully compatible with LPG equipment. Moreover, it is preferable for winter operation, as it does not freeze and ensures stable operation of the gearbox. The only caveat is that propane is more expensive than a propane-butane mixture.

    Why do some gas stations refuse to fill gas in winter?

    This is due to the fact that at temperatures below −20°C the butane in the mixture stops evaporating, and refilling becomes impossible (gas does not enter the cylinder). The solution is to look for a gas station with heated tanks or refuel with propane.

    Is LPG harmful to the catalyst?

    High-quality LPG (without sulfur impurities) is less harmful to the catalyst than gasoline, since it burns more completely and does not contain lead. However, if the gas contains sulfur or heavy hydrocarbons, they can shorten the life of the catalytic converter.

    Is it possible to mix gas from different gas stations?

    Yes, but not recommended. If you fill with propane at one gas station and a mixture with a high butane content at another, stratification of the gas in the cylinder may occur. As a result, propane will be consumed first, and then butane, which will lead to unstable engine operation.

    Which gas is best for turbocharged engines?

    For turbo engines, octane propane is recommended 110+ or a mixture with a minimum butane content (no more 20%). Butane has a lower octane rating and can cause detonation under high loads.