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Fuel is a huge part of the performance of your vehicle, and is unfortunately one of the least considered aspects of it’s running. The casual motorist takes gas for granted. Its ubiquitous, pretty similarly priced, and sometimes just another chore that is part of vehicle ownership, right?
Wrong. No matter how well engineered your vehicle is, to keep it running well proper maintenance and the right type of gasoline are essential. Unleaded gas is classified according to octane rating. In the US we have 87 (regular) 88-90 (mid) and 91-94 (performance). Often, they are not all available at one specific gas station.
So, what exactly does this rating mean? Will you damage your auto by mixing 87 with 92 octane? Which number is the best for you? In this article we’ll answer those questions and more.
Octane Rating Explained
Octane rating refers to the percentage of an organic molecule called iso-octane that is commonly found in gas. This one molecule is fairly important as it regulates the controlled burning of the fuel in your engine.
How does It Work?
In the internal combustion cycle the air and fuel mixture is compressed inside the cylinder and then ignited by the spark plug at a very critical position so as to maximize the torque transmitted to the crankshaft. This assumes though that the fuel air mixture only ignites on the spark from the sparkplug.
What’s That Knocking Sound?
Sometimes things can get a little ahead of themselves and the mixture spontaneously ignites before the spark. Of course, this would be at the wrong time for what the engine requires, and the result is a pinging noise or engine knock. Usually this does not damage the engine, as it is designed to tolerate it happening, but prolonged knocking cycles can completely destroy the pistons and other mechanical parts of the engine which can lead to a costly rebuild. That is where iso-octane comes in. Basically, the higher the concentration of iso-octane in gas, the more pressure it can withstand without spontaneously igniting and causing an engine knock. This is essential for almost all performance engines which use much higher compression ratios then your vanilla daily drivers.
Fortunately, modern cars are largely computer controlled, and designers have included a clever knock sensing system. This detects the uneven vibrations that occur when knocking happens and decreases cylinder pressure or retards the spark timing to compensate for the knock. This does tend to reduce your engine performance.
Which Octane Rating Is Right For Me?
The type of gas you should use largely depends on what you are planning on doing with your auto. Some of us only have one car that is the daily during the week and gets opened up on weekends to get the blood flowing. In that case, you’d want to stick somewhere in the midrange of 88-90 research octane number (RON). If you’re only using the car for street or track stuff, then the premium range is best for you, but as a daily driver only, it will suit your wallet better to stick with the lower octane ratings. It’s not the best practice to mix two different ratings of gas, but if you have to, your vehicle will be able to compensate for it, but rather try to add a higher octane gas to a lower one if possible. Also remember that not all gas stations are created equal; try to go to one that is always busy – that way you can be assured of getting gas that hasn’t sat around in the underground storage tanks for too long.
If you’re still unsure of what type of gas is best for you, why not look at what your manufacturer recommends? Alternatively pop into our Pompano Beach automotive shop, Foreign Affairs Motorsport for friendly advice. You don’t even need to knock.