Difference Between Gas and Petrol

The key difference between gas and petrol is that the fuel consumption is very high in operating vehicles with gas when compared to that of petrol.

Although the term gas refers to the gaseous state of matter, in industrial chemistry, we use it as a common term for liquefied petroleum gas or LPG. The term petrol refers to gasoline. Both these compounds consist of hydrocarbons, and both are useful as fuel.

CONTENTS

1. Overview and Key Difference
2. What is Gas
3. What is Petrol
4. Side by Side Comparison – Gas vs Petrol in Tabular Form
5. Summary

What is Gas?

Gas is an industrial term for LPG or liquefied petroleum gas. It is a flammable mixture of hydrocarbons. It mainly contains propane or butane or a mixture of both compounds. Hence, it is a common fuel that we use in heating appliances, cooking purposes, etc. Furthermore, we can use it as an aerosol propellant and as a refrigerant as well. Mainly, this is because it can replace chlorofluorocarbon (CFC) compounds. If we use this gas as a vehicle fuel, then we name specifically as “autogas”.

Apart from propane and butane, there can be some fractions of propylene and butylene as well. However, the amount of propylene should be less than 5% in order to use it as autogas. To detect leakage easily, manufacturers add a powerful odorant such as ethanethiol.

We obtain this fuel entirely from fossil fuel via refining petroleum oil. This fuel burns cleanly with no soot. But, it may have very few sulfur emissions. Since it is a gaseous mixture, it does not account for ground or water pollution, but air pollution.

Since the boiling point of LPG is below the room temperature, it can evaporate immediately after its exposure to normal air. Therefore, usually, it is available in pressurized steel vessels. However, we should not completely fill the vessel (only 80-85% filled) in order to allow for thermal expansion of the liquefied gas.

What is Petrol?

Petrol is the common name of gasoline. Gasoline is a liquid fuel that we use mainly in spark-ignited internal combustion engines. It is transparent and is a petroleum-derived fuel, which leads to its name petrol. It contains a mixture of lightweight hydrocarbons with some additives added to enhance the desirable properties. We can produce gasoline from crude oil; typically, 42 gallons of crude oil yields about 19 gallons of gasoline.

Usually, the mixture of hydrocarbons in this fuel contains molecules ranging from C4 to C12. Thus, it contains the hydrocarbons consisting of 4 carbon atoms to 12 carbon atoms in their chemical structure (lightweight hydrocarbons). In brief, gasoline is a homogeneous mixture of these molecules including paraffin, olefins and cycloalkanes.

What is the Difference Between Gas and Petrol?

When operating vehicles with gas, fuel consumption is higher than that of petrol. It is the key difference between gas and petrol. Moreover, the energy output is lower in gas compared to petrol. However, gas is a lot cheaper than petrol, and that offsets its high consumption. As another important difference between gas and petrol, we can say that petrol combustion is partial, resulting a lot of carbon dioxide and other particulate matter in the emissions while gas is comparatively cleaner, and emissions are less than petrol. Therefore, gas is more environmentally friendly and economical to use in vehicles than petrol. However, a lot of people are still using petrol for their vehicles, therefore, gas is less available than petrol in filling stations. Although gas is more efficient than petrol, we cannot observe its efficiency unless if we optimize the engine design for LPG fuel.

The below infographic summarizes the differences between gas and petrol.

Summary – Gas vs Petrol

The term gas is an industrial term that we use to name LPG or liquefied petroleum gas. Petrol, on the other hand, is the common name for gasoline. The key difference between gas and petrol is that the fuel consumption is very high in operating vehicles with gas when compared to that of petrol.

Reference:

1. “Liquefied Petroleum Gas.” Wikipedia, Wikimedia Foundation, 25 Aug. 2018. Available here
2. “Gasoline.” Wikipedia, Wikimedia Foundation, 2 Nov. 2018. Available here  

Image Courtesy:

1.”Liquefied petroleum gas cylinders”By Krish Dulal – Own work, (CC BY-SA 3.0) via Commons Wikimedia  
2.”GasStationHiroshima”By No machine-readable author provided. (Public Domain) via Commons Wikimedia