Octane Vs Petrol – Which Is The Best Fuel For Motorcycle?

Saleh Md. Hassan
April 8, 2013

Hello riders, here I am motivated to focus on motorbike fuel. Octane Vs PetrolWhich Is The Best Fuel For Motorcycle? Which we  will use to run our bikes. I am quite sure of your agreement with me about the importance of that as it is directly related to your pocket and mobility of your bike. Most of the motorbikes in our country run by petrol or octane.

octane vs petrol

There is a little numbers of diesel engine bikes in army (out of order) and there are also some electric bikes which run over the country powered by electric motors. Here my focus on petrol (gasoline) engine bike.

There are two category petrol engine bikes: 2 Stroke and 4 Stroke. Both are very popular in our country. Both of them uses near same technology (internal combustion) to make power from fuel.

Here somewhat I will go slightly for core technical issues but discuss mainly on the fuel that we use, and how can we gain maximum utility from the fuel considering our local scenario.

octane vs petrol which is the best in bangladesh

Octane vs Petrol – Our Fuel (In Bangladesh)

First we need to know about our fuel octane vs petrol, what we are using and what its standard is. In Bangladesh there is huge lack of information. Most of the situation general people lives out of real information. Whatever, commonly we use petrol and octane for our motor bikes.

Most of the people think petrol and octane is two different type of fuel. But by the name petrol and octane actually there are no differences. Both are internationally known and commonly named as “Gasoline” and chemical construction is also same (C8H18).

So we can call it Gasoline or Petrol or Octane. Internationally there is also some category of gasoline/petrol/octane it differentiated by a quality rating number, called OCTANE NUMBER or RON (Research Octane Number).

Internationally the standard rating of gasoline starts from Octane no 86 (RON 86) and goes over 91 and even 102. These different rated gasolines are all same gasoline with same chemical construction.

But difference is about their enhancing additive and detergents, some of which boost fuel capability (capability of huge expansion, compression and controlled combustion) of making smooth combustion mechanism in cylinder (no hiccup or knocking sound from piston, valve or connecting rod or regression/ back force tendency). Here I will use the word Gasoline generally to mean the fuel Petrol or Octane.

how octane vs petrol work

Octane vs Petrol – Fuel Action Line

To understand the need of quality fuel we need to know the basic line of fuel action. After mixing the air and gasoline the mixed vapor injects to the cylinder/combustion chamber, then the piston compresses the mixed vapor and the spark plug fires the mixture, then the mixer makes a huge boom of gas and the gas expanded with forces and pushes the piston out of the cylinder.

Here the fuel needs some extra capability to be expanded and compressed hugely, but in a controlled ratio to make the whole combustion mechanism smooth and controlled.

Other wise the combustion will not be controlled and power production ratio will not be equal every cycle (uncontrolled) and thus the piston, connecting rod and valve activity will hampered and make metallic noises like piston hiccup, knocking sound from valve and connecting rod etc. (Internationally this noise is called Engine Knocking). And also the engine can make regression or back force tendency and can vibrate a lot.

Octane vs Petrol – Leaded Gasoline

In the earlier stage, old model gasoline engine was not high performer engine. So they could be run with simple gasoline. But day by day the gasoline engine action and performance improved, and it needed smooth and controlled combustion for vibration free and high speed performance. So some extra but controlled quality needed from the gasoline.

So the researchers researched and found that the Lead (Pb) can be used as booster for the gasoline to increase the fuel capability. As it is one of the cheap & best boosters for gasoline, so lead has been used with gasoline world wide till the end of 20th century. And it is known as Leaded Gasoline. But it started to be banned to mix lead with gasoline at the end of 20th century due to its direct and indirect harmful affect on nature and human.

Octane vs Petrol – Unleaded Gasoline

Due to the harmful affect of lead (Pb) on human and nature, there was a activity to ignore the use of lead with gasoline, and recommended to use other additive as booster for the gasoline to keep the gasoline capability in that level (RON) which can be gained by the lead. So researchers started to use other alternative additives instead of lead and it called as Unleaded Gasoline.

octane vs petrol lead

Octane vs Petrol – Leaded or Unleaded and Why

This question is not related to the common gasoline user of our country and can be elaborate in different writing (maybe Fuel Booster). But for the interested user I should touch this point at least a little. Lead is a very economical & huge effective boosting additive, which can boost gasoline capability hugely. And it is very much easy to gain the higher RON by adding Lead with Gasoline.

So in earlier years it frequently used to boost the fuel capability. And still in racing vehicle, in aviation fuel and in some limited countries it is used with fuel [and there are other things like Nitrous Oxide (NOS) to increase the engine power for limited time].

But the lead has huge and long term bad impact on human body and nature. So we should avoid leaded additive and gasoline. And there is nothing to be disappointed with unleaded gasoline. The modern lead free gasoline has the capability to run your bike or car engine with optimum performance.

And if you are hardcore rider you can go for other lead free external additive if you confirmed about their efficiency and find those in Bangladesh, and of-course if you have the higher performance vehicle.

RON (Research Octane Number) – Octane vs Petrol

RON is an important term of gasoline to concentrate. When the gasoline engine getting modernized and needed more capability from gasoline for increased and controlled performance, then some additive and boosters used to raise the gasoline capability level to gain the controlled high performance. And Lead was the best boosting additive for the gasoline, which can raise the gasoline capability in standard level.

But the poisonous affect of lead revealed and researchers researched out other alternative booster like ethanol, methanol, toluene and other additive (costly and less powerful than lead), which can boost the capability of gasoline in controlled way and they have the minimum harmful affect on nature.

Hence finally internationally it authorized to add ethanol and other additive with the gasoline to keep the capability level in a standard. They set some capability standard of the gasoline considering the additive limit and fuel capability. And this is the Octane Number or RON (Research Octane Number).

octane vs petrol company in bangladesh


Octane vs Petrol – Scenario of Gasoline In Bangladesh

By the international law, it is mandatory to stick the RON label on the dispenser machine of gasoline, so that people can know for which quality of gasoline they are paying for. And there are more than one type of gasoline in the fuel pump, which are fully noticed by yellow RON sticker like RON 87, RON 91 or Octane 87, Octane 91.

Unfortunately in our country Bangladesh we never have seen such informative fuel pump anywhere. But though we do not know the RON of our gasoline, we use two type of gasoline with two rank of RON. They are known to us as “Octane & Petrol” (like “Mom & Mother”. . . . funny!). Now it is the question, what the RON of our gasoline (octane & petrol) is.

In this writing, earlier I mentioned the minimum RON of international standard is RON 86 and goes above RON 91. So we can predict, our Petrol is RON 86 at least and Octane can be RON 87 or more. But in my finding I could be sure that our Petrol RON is only 80 and Octane RON is 95.

And more over I found some topic about the proposal to the ministry to increase the RON of petrol from 80 to 86 before increasing the price and in consideration of natural affect. Though most of the gasoline user do not know about the RON but there is a common question “Which should they use from Petrol vs Octane and why?” And I will add, “For which bike?

octane vs petrol fuel pump

Octane vs Petrol- What Should We Use ?

 If you in dilemma about octane vs petrol then its for you. If our petrol would have the RON at least 86 then we should not need to go for higher rated fuel. Generally till today our petrol RON is 80. So it is bellow from international standard. So normally we can say it cannot be used for our bikes. But in real scenario it’s not quite true.

Do most of user in our country uses high performer bike?  Answer is No. Most of us use only bellow 150 cc bikes; which are designed with single cylinder, single piston, with only two valves, with the compression ratio bellow 9:1. And some of their engine making quality is also very economical that nothing can improve their performance.

And there is a huge quantity of two stroke bike in our country. So our petrol with RON 80 is quite ok for our regular four stroke bike. And two stroke bikes do not need more (I have ridden my Honda H100S CDI several time with kerosene accidentally). But you should be confirmed about the petrol, whether it is really RON 80 or it has not mixed with kerosene or with other contaminant.

In our country it is very much common to make contamination petrol with kerosene, thinner or other things in rural areas (even in Dhaka). So in such situation we do not getting the pure petrol at least. So we should be watchful for this. This type of contaminate petrol can damage the engine. So a question arises, is there any way to be sure about the purity of the petrol? Yes, a little. It will be discussed later.

Octane vs Petrol – Available Octane Type In Bangladesh

 Now I am going for the Octane. Our octane is RON 95 or Octane95. Now there is a question where should this octane be used? Yes hopeful thing is that there are some high performances bikes are entering in our Bangladeshi market.

The most of 150cc and higher displacement bike in our country have the performer four stroke engines. Those engines are designed with higher compression ratio, and also sometime with more than two valves.

And they required for standard or regular gasoline (internationally at least RON 87) where our petrol is only RON 80. So we can use our octane for those bikes. And there are some climate variations in our country.

In the winter season most of area of our country, weather remains very much cold. So our petrol cannot give effective performance for those engines. And there are huge ignition problem in the cold weather. So those engines need a little higher rating octane.

Octane vs Petrol – Using Petrol with Octane:

There is common malpractice in our country among the bike users to mix petrol with octane in various ratios like 1:1, 1:2. Most of them has no clear concept what they are doing and why. They only do that with some miss concepts, and don’t know whether their bike needs petrol (RON 80) or octane (RON 95) or something else.

Generally two different RON rated gasoline can be mixed to get the average RON rating like (RON80+RON95)/2=RON 87.5. Yes this can be done when the two different RON rated gasoline are composed with same type of booster, detergent and antioxidant additive only.

But in Bangladesh we are not sure about our Petrol & Octane additive composition and whether they have composed with same type of chemical additives or not. So it is not only better but also best not to mix petrol with octane in any ratio. But is our petrol is pure RON 80 every where and have not mixed with other bad contaminant like kerosene?

So especially in such situation we can go for only 1:1 ratio (50%:50%) for the average performer bike. In that case use petrol first and observe your bike performance, if needed then go for octane. And again observe for the performance change. If something bothering you then go for 50%:50%. Again observe and take final decision considering your bike performance.

This concept is not for high performer bike. Use only octane (RON95) for them with out mixing any type of external boosting additive.


Does Our Octane Over Heat Motorbike Engine?

Yes, this is an issue in consideration of the quality of engine. You need to know does your engine need higher RON or not. If your bike is with bellowing 150cc engine with compression ratio bellow 9:1 then you can use only petrol confirming its purity. Other wise go for 50%:50% (Octane : Petrol) and it is also considerable in winter season.

Using higher RON gasoline would really overheat the engine especially at summer season and can damage in the long run. But when your bike has a high performance engine with wider compression ratio, then use only octane (RON 95). It will never over heat your bike engine.

Engine over heats, when its compression ratio is lower and you are using higher compressing as well as higher booming gasoline (higher RON). So lower cc & lower compression ratio engine should use lower RON and higher performer should use higher RON gasoline.

octane vs petrol ron

Octane vs Petrol – Should new bike use lower RON ?

This is also a misconception. People thinks new bike should use petrol (lower RON) and older should use octane (higher RON). But it is good to use better RON gasoline for the new bike for the ‘Break In’ (run in) period (first 2,000 km).

As in break in period the speed limit is low, RPM is low and also trip is shorter, so no scope for overheating the engine. More over engine gets perfectly heated and internal parts get perfectly polished. So don’t hesitate using octane in your new motorbike at least for first 2,000 km.

Do we need to go for higher RON gasoline when using a lower RON ?

If you search in web you will find no one encourage going for higher RON octane than recommended from the bike manufacturer. When you feel the need to go for higher RON, then you can use it to gain specific utility.

And yes, when your bike engine grew old with mileage and you have replaced the piston with largest size as the cylinder decayed and  expanded by extreme use, then you can switch to higher RON (if needed).

But when you have replaced with same size piston with filling the cylinder gap then you don’t need to go for higher RON gasoline. Use higher RON only for the break in period of newly installed parts.

Another thing, when the engine noising a bit, maybe the piston, piston ring and the cylinder are a little decayed, then higher RON gasoline can do a little job against the noise but reduces the bike mileage.

So it is better to replace the faulty parts and use the gasoline what you are using before. And in winter season you can use a little higher RON to reduce ignition problem.

Fuel Booster & Detergent Additive – Should I Use ?

Manufacturer does not recommend for any type of external fuel additive and booster for their bike engine. But some of us like hardcore user tends to add some fuel booster, detergent additive for there bike. Most of the time; they are harmful for the carburetor/injector, engine and catalytic converter.

When they are used for long time they corrode the sharp edge of the piston, valve cylinder body and damages spark plug and catalytic converter. So those are only to be used in sports bike to gain short time utility.

So it is better to avoid them and take care of the bike with regular routine maintenance. And if possible go for higher performance engine bike or modify the engine with the help of experienced technician.

Though RON rating is fundamentally not related to the power production of gasoline in combustion chamber but in practical situation it related to engine performance maybe it bad or good, considering the quality of engine. So considering the real activity I hereby illuminating bellow two heading:

Using higher RON gasoline in low performance engine – Any Problem?

This is just wastage of money as well as fuel. You will see the engine getting started fast even in cold weather with a deep sound and throttle responding immediately, but no need to be happy as it will reduce the bike mileage.

Engine will get over heated. Top speed could be gained easily but reduce engine life creating over pressure in combustion chamber (cylinder). Sometime pre-ignition occurs, or some time engine misfire with huge sound over silencer and the piston, piston ring, connecting and the cylinder will ruin soon.

spark plug for bad fuel


Using lower RON gasoline in high performance engine

Engine will not ignite properly even pulling the choke lever in hot weather. Combustion will not perfect and smoke will seen at the end of exhaust. Engine will sound harsh and make metallic noises like piston hiccup, knocking sound from valve and connecting rod etc.

Here little high mileage gained but engine gets over heated. Throttle will not respond fast and looses its smoothness and sometime engine gives back force tendency and vibrate. Top speed could not be gained properly. Spark plug will oily & carbonized soon and engine will misfire.

bad fuel impact in motorcycle

Octane vs Petrol – Using Contaminated Gasoline:          

In our country most of the time we remains out of pure fuel. Most of the time we had to use contaminated fuel. Contamination does a little problem for the diesel driven engine.

But in terms of gasoline engine like motorbikes (which are designed with most sophisticated lower displacement engine) contaminated gasoline has a very bad impact. Sometime we have no choice rather use those gasolines (petrol or octane). In that situation RON rating remains out of range. Whatever if we use those type of fuel then:

1                 Engine will not ignite fast. Several attempt will needed to start the engine even choking at hot weather.
2                 Engine could misfire due to improper combustion. smoke will seen at the end of exhaust
3                 Throttle response will be late and will make a back force when accelerating the throttle.
4                 Engine will make harsh noises, sometime like piston hiccup, knocking sound from piston ring, valve, connecting rod etc.
5                 Engine will vibrate.
6                 Engine could stop suddenly ridding in higher speed.
7                 Top speed will not be gained.
8                 Engine will loose all of its smoothness.

motorcycle piston valve

You can be sure more about contamination when:

1                 Spark plug gets carbonized frequently
2                 Spark plug gets burned dark black color(in perfect combustion with solid fuel it gets burned ash or burned brown color)
3                 Spark plug will be oily .(in perfect combustion with solid fuel it will not be oily)
4                 Spark plug damages soon.
5                 Cylinder head piston head, valves will be carbonized soon. And there will be oily sediment with the carbon.
6                 Exhaust will sound bad and produce more smoke even in four stroke engine.
7                 In case of four stroke bike exhaust pipe can through out a little oily smoke (two stroke engine does it frequently)

In such case just change the oil with cleaning the carbonized parts. And of-course drain the contaminated fuel from carburetor loosing the draining screw below the carburetor.

how to test motorcycle fuel

Testing a Gasoline for Quality:

There is no way to test the purity of gasoline without the laboratory test. But from the above mentioned symptom can assure its impurity. And you can do a little by own to test the workability of certain gasoline. Just collect some gasoline (petrol or octane) from the source. Take a little gasoline in your hand and rub it with two hands.

When the fuel vaporized take a keen look to your hand. If your hand seems dry then the gasoline is ok. But if there an oily sediment or residue found, then it has been mixed with some other contaminant like kerosene or diesel. If your have a keen smell then take a smell of your hand. Maybe you can be sure if it mixed with kerosene or diesel or turpentine oil.

Another way, take a steel plate. Drop some gasoline on the plate and fire it throwing a match sticks. When the gasoline burnt off and the plate temperature become normal then observe for the oily sediment and take smell for the contaminant.

So riders, hope this writing may help you to know more about Octane Vs Petrol. Thanks for your patient concentration on this writing. I will be happy for your further quarry, suggestion or addition and also for your valuable comments.

Information courtesy: Wikipedia (the free encyclopedia), The Federal Trade Commission, Petro-Canada,,,, The Economist, Eastern Refinery Ltd, Atlas Bangladesh Ltd.

Image courtesy: Wikipedia (the free encyclopedia),, Bangladesh Petroleum Corporation.

By Saleh MD Hasan

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