High-performance vehicles rely on engines that work differently from standard ones. For one thing, those powerful engines place their combustion chambers under much higher pressure than usual. This condition requires a special kind of fuel.
High-compression engines need high-octane fuel. The higher compression ratios will cause regular fuel to ignite prematurely, resulting in extensive damage to the engine in the long run. High-octane or ‘premium’ fuel is much more stable under higher compression ratios, thus making it more suitable for such engines.
This guide will help you understand how compression works in an engine and why high-octane fuel is crucial for engines with higher compression ratios.
Let’s get started.
What Is Compression in an Engine?
When you want to understand the relationship between high-compression engines and high-octane fuel, it’s crucial to recall some basics of internal combustion engines.
Firstly, compression happens when pistons rise inside the engine's combustion chambers. As the term suggests, the rising piston compresses the air/fuel mixture to prepare it for combustion.
Like those on your favourite sports cars, cars with high-performance engines compress the air/fuel mixture much more than a regular engine would. That’s why they're called 'high-compression' engines.
You can compare the compression of one engine to another by using the compression ratio. We calculate engine compression ratios by measuring the engine cylinder volume's difference before and during compression.
Simply put, a high-compression engine has a higher compression ratio than a standard engine.
How Is a High-Compression Engine Different?
High-compression engines force the air and fuel mixture into a much smaller space before combustion. That can produce many different benefits, including the following:
- Higher power output
- Lower fuel usage to produce that higher power output
- Less exhaust gases coming from that process
Those benefits result from a more intense combustion process in the high-compression engine.
Unfortunately, the higher intensity also places a lot more stress on the engine, causing more heat and friction that exposes the engine to increased wear.
Thus, due to the more violent combustion inside the chambers and the added stress it causes, high-performance engines need a fuel that can keep up.
That fuel must cope with the higher compression ratios while helping to manage heat and minimize wear.
What Is the Best Fuel for High-Compression Engines?
The best fuel for high-compression engines is a high-octane fuel, i.e. those with RON 95 or higher.
High-octane fuel is typically marketed as ‘Premium’ fuel because it costs more than standard fuels. I’m sure you’ve seen these numbers on the bowsers.
Premium fuels cost more because they’re stable in higher-compression situations and include additives meant to keep those engines operating efficiently. In simpler terms, they won’t ignite prematurely despite being compressed much more intensely in an engine, which is not the case with regular fuels.
The difference between standard and premium fuel is measured by its research octane number or RON. Premium fuels have an octane rating of RON 95 and above. A standard fuel octane rating is anything below that.
What Are the Benefits of Using Premium High-Octane Fuel?
Premium or high-octane fuel is a necessity for high-compression engines because it can cope with the violent combustion in those engines.
Moreover, high-octane fuels often include additives not found in standard fuel.
Here are some of the benefits of premium high-octane fuel:
#1 No Premature Combustion
First and foremost, high-octane fuel prevents premature combustion or ‘knocking’. Typically, the compressed air and fuel mixture in an engine chamber is ignited by a spark plug.
However, less stable fuel will prematurely combust even before the spark plug does its job, like in a diesel engine.
That will cause knocking, which is unhealthy for the engine in the long run.
Since premium high-octane fuel remains stable despite high compression, it doesn’t combust prematurely and allows the engine to function as it should.
#2 Maximized Power Output
Premium fuels help maximize an engine’s power output. You may have heard that high-octane fuels increase engine power—that’s not the case. What happens is that the fuel’s stability under pressure and the additives help the engine work optimally.
So, it doesn’t increase the engine’s power output per se, but rather help the engine perform as efficiently as designed.
#3 Removes Carbon Deposits
Some additives included in premium fuel help keep the engine clean inside. More specifically, they remove carbon deposits that naturally build up inside any internal combustion engine.
#4 Overall Better Fuel Economy
An engine that works optimally (due to the high-octane fuel it uses) results in better fuel economy. The engine burns less fuel, and a full petrol tank lasts longer than it would otherwise.
What Happens If the Wrong Fuel Is Used in a High-Compression Engine?
Feeding standard or low-octane fuel to a high-compression engine isn't necessarily fatal. Filling a petrol tank with diesel won't get the same outcome.
Still, it's not something you want to do repeatedly as it can cause significant damage in the long run.
Remember: Low-octane fuel isn't stable when placed in a high-compression engine chamber. It will cause premature combustion, reducing the engine's overall efficiency and damaging it in the long run.
So, drivers must refer to their car owner’s manual to ensure that they are using fuel with the correct octane levels.
To learn more about engine and fuel types, check out the Blog at CarpartAU.
By Ray Hasbollah