This article is a rebuttal of Paul Tan's "Research Octane Number: What is RON95?", which contains several misleading information.
RON is actually short form for Research Octane Number. It is a rating for unleaded petrol. Higher Research Octane Number mean the petrol have higher resistance toward pre-ignition or detonation. In very basic terms, it's a measure of how hard the fuel is to ignite.
If you run your vehicle on low octane petrol you might notice a 'knocking', 'rattling', or 'pinging' sound (as it’s often called), which means the fuel is detonating instead of burning smoothly. This is not only a waste of energy, but it can also damage your engine in the long run. Burning is the desired effect of any internal combustion engine (not an explosion per se).
Fuel with a higher octane number suitable for your vehicle's engine will eliminate knocking. Older cars that were designed to run on a lower RON fuel can also benefit from a higher RON, because the older the car and the higher the kilometres, means the engine will have a greater propensity to knock. This is mainly caused by a build-up of contaminants and carbon deposits which, when hot, can cause pre-ignition.
Lower RON numbers means the fuel is more likely to ignite spontaneously, in minor accidents.
In a gasoline engine, ignition is controlled by adjusting the timing and/or intensity of the spark. Providing a spark at exactly the right moment gives you maximum power and efficiency and minimizes pollution. But any compressed air-fuel mixture will spontaneously ignite, or "detonate." This is also known as "knocking," and can destroy your engine in addition to damaging your bank account and the environment. We want gasoline to burn when the spark plug fires, but not when the piston compresses it.
What does this mean to you? If you drive a high-performance sports car that uses high compression and high RPMs, you probably have a minimum safe octane rating for your engine. Using fuel with too low an octane rating may cause your engine to fail prematurely.
Knock Sensors
Some engines are fitted with a device called a knock sensor. Regardless of whether your vehicle has a knock sensor or multiple knock sensors, if it has high mileage, a higher RON fuel would be the most mechanically sympathetic thing to do. Why is that?
You see the knock sensors in your engine (if equipped) have a job to do. They protect your engine from knock by retarding timing; but here is the thing - your car ‘has’ to knock first before the knock sensors can do their job! This is not a good start in the first place. When an engine ‘knocks’ the engine temperature soars, and with most modern engines using an all alloy block, heat is bad... very bad.
Of course, modern cars have very advanced fuel control systems and can deal with a much greater variety of fuels than old carburetor models.
The manufacturer of your car does not get kickbacks from the oil companies, and they do not benefit in any way from you spending more money on gas. However, they do see fewer damaged engines that have been run on high-octane gas so they are reasonable in suggesting that you use it.
It may also be that people who spend more money on fuel generally have more money to spend, so they are more likely to conduct regular maintenance and keep their car happy.
Bottom line: If you hear knocking (it's a subtle noise, you might want to get a mechanic to demonstrate it for you), use a higher octane gas. It happens most frequently when climbing a steep hill under heavy acceleration. It can happen to cheap clunkers too and is just as destructive.
So what does all this RON nonsense mean to the average motorist? Does it give you more power like many people suggest? Can you really ‘feel’ that extra power via the driver’s seat? Does a higher RON fuel equal better fuel consumption? The answer to these questions is somewhere between “maybe” and “yes”, but it depends a lot on your car, its state of tune, and how you drive.
Will lower quality petrol damage the engine?
This depends on your vehicle’s engine compression ratio. The compression ratio is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. Higher compression ratios will however make gasoline engines subject to engine knocking if lower octane rated fuel is used. This can reduce efficiency or damage the engine.
The compression process caused temperature variation inside the combustion chamber. This will lead to premature ignition of oil, which we refer as knocking. Heavy knocking occurs equal to low performance, equal to serious engine damage as well. The main point here is you must select the petrol with RON suitable to your engine compression ratio.
My advice is reach for the better stuff. Not only are you “spreading the love” to your engine, but you will likely see better mileage and you will be doing your bit for the environment. On the whole, the higher the RON, the cleaner the emissions.
Till next time, Happy and safe motoring.
References:
- http://answers.yahoo.com/question/index?qid=20100928094016AA2ts2x
- http://www.icalvyn.com/ron95-petrol-called-research-octane-number-95/
- http://auto.howstuffworks.com/engine1.htm
- 006 Article by Paul Tan: 2 Research Octane Number: What is RON95?
- Fundamentals of motor vehicle technology by Hiller and Coombes
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