Difference Between Unleaded and Premium Unleaded

Unleaded vs Premium Unleaded

Petrol is a volatile liquid form of hydrocarbon fuel. It is isolated by fractional distillation of petroleum and is used as a fuel in the internal combustion engines. Additional compounds have mixed with petrol in order to enhance its usage in engines. Hydrocarbons like isooctane or benzene and toluene are added to petrol, to increase its octane rating. This octane number measures the ability of an engine to cause self ignition in the engine cylinders (which causes knocking). In premature ignition, when petrol and air mixture are caught before the spark is passed from the spark plug, it pushes against the crankshaft producing a knocking sound. Because of this knocking, the engine tends to overheat and loose power. Therefore, it damages the engine in the long run. Therefore, to reduce this, the octane number of the fuel has to be increased. Other than adding hydrocarbons stated above, the octane number can also be increased by adding certain lead compounds. This will increase the octane number; thus, petrol will be more resistant to self-ignition, which causes knocking. Furthermore, adding lead compounds is a cost effective and efficient way to reduce this problem.


This is a type of petrol, which does not contain lead. Lead compounds are normally added to petrol, as an anti knock agent as stated above. Lead is highly toxic to humans and other animals. When lead compounds are burned in the engine lead particles will come out with the fumes. They will be accumulated in the respiratory tracks of organisms causing health problems. In the extreme conditions, lead can be carcinogenic. Furthermore, it causes environmental pollution. Because of these reasons, lead containing petrol are now banned from usage and replaced by unleaded petrol. Unleaded petrol does not produce harmful fumes containing lead.

Various strategies have been used to eliminate the knocking problem in vehicles by using unleaded petrol. One solution is by adding aromatic hydrocarbons to increase the octane rating. However, this octane rating is little lower than in leaded petrol. Another way is to produce engines, which do not cause pre ignition, and car manufacturing companies have produced engines with better fuel burning techniques. Cars with catalytic converter are an example, and these cars use unleaded petrol.

Premium Unleaded

Premium unleaded petrol is petrol with higher octane rating. Normally, the minimum research octane number for premium unleaded should be 95; therefore, it is expensive. In addition, the car engine should be modified to utilize this fuel efficiently. Otherwise, just using this fuel in a normal car does not give a benefit. On the other hand, if the car is designed to use premium unleaded petrol, by using regular unleaded petrol, the car will be damaged. Therefore, if the car is specifically designed to use premium-unleaded petrol, you should use petrol with a higher octane number, which is more than RON 95.

What is the difference between Unleaded and Premium Unleaded?

• Octane rating in premium unleaded is higher than in normal unleaded. For unleaded petrol, the minimum research octane number (RON) should be 91, whereas, for the premium-unleaded petrol, it should be RON 95.

• Premium unleaded is more expensive than the unleaded petrol.

• If a car is designed to use premium unleaded petrol, by using regular unleaded, the engine can be damaged, or the performance can be much lower.

• When premium unleaded petrol is used, fuel consumption is lower, and the power is more than what you get when unleaded petrol is used.