Car gas


January 27, 2022

Automotive gas, also known as LPG (Liquefied Petroleum Gas) or LPG, is a mixture of liquid hydrocarbon gases used as fuel for motor vehicles. Household heating and cooking cylinder gas with almost the same composition is commonly referred to as LPG for short.


The liquefied gas may be propane, butane, propylene, isobutane, isobutylene, butylene, and mixtures thereof. Its properties are defined in the MSZ EN 589 standard. Liquid motor fuel has almost the same composition as household LPG. Compared to household LPG, for example, car gas may contain less pollution and may not contain hydrogen sulfide or water. It is obtained from mined hydrocarbons during refining, practically as a by-product. The liquefied gas contains 95% propane (C3H8) and butane (C4H10). The remaining 5% consists of heavier hydrocarbons. The ratio of propane to butane is about 40% -60%.

Storage, transport

It can be liquefied at a relatively low pressure (approx. 6 bar) at ambient temperature. It is thus transported on tankers to fuel wells and stored in the tanks of filling stations until weighed. It is filled into the car's tank with a pump via a special filling valve. In the tanks of cars approx. The liquefied gas is stored at a pressure of 12 bar.

When using information

If the liquefied gas is released into the open in a liquid state, it immediately begins to evaporate. During evaporation, its volume is approx. It grows 230 times and cools its environment greatly, from which it draws heat when it evaporates. Around the opening, where the gas escapes or where the liquid gas collects outdoors, the moisture content of the air condenses and may freeze. Exhaust liquefied gas creates a mist in the vicinity of the gas jet. In this case, the liquid fuel may cool down to such an extent that its evaporation may stop temporarily.

Possibility of danger

Many believe that car gas and a gas called “11.5kg” of LPG used for cooking are the same and try to fill their bottles in an LPG well, but this is illegal because cars have a tank of at least 25-30 bar, while PB -bottles are designed for lower pressures and no safety fittings are provided; they should only be recharged under controlled conditions.


The properties of the liquefied gas at tank pressure stored in the tank are as follows: its density is 0.525… 0.56 kg / l lower calorific value 24.7 megaJoules / l thermal expansion at 10 ° C approx. 4% boiling point at atmospheric pressure: -5 to -42 ° C Vapor pressure at -5 ° C of at least 2.5 barThe main properties of gaseous liquefied petroleum gas at atmospheric pressure are as follows: relative density: 1.8… 2; density: 2.2.7 g / l; ignition temperature: 490… 510 ° C; lower-upper inflammatory concentration: 2… 9 vol%; flame propagation speed: 32 cm / s; lower heat value: 0.105… 0.110 MJ / l; Amount of air required to burn 1 liter of LPG: approx. 28 liters; engine octane number: at least 89 (approx. 100).

Special features

A special feature of liquefied gas is that the tank pressure is primarily determined by its temperature. Depending on the temperature, the tank pressure varies over a wide range. It can be said that the tank pressure can vary between 3 and 15 bar at ambient temperature. In summer, the pressure in the gas tank of a car parked in the sun often reaches 16-18 bar. At winter temperatures of -10 ° C, the tank pressure can drop to 2 bar. Physiological effects Contains no toxic substances. Inhalation, although not toxic, should be avoided due to the physiological effects of the odorant. If a large amount of car gas is released into the air, it will lack oxygen

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