Cheaping Out On Regular Gas Could Have Unforeseen Consequences

By John Tallodi

We all want the best for our cars, but recent fuel price hikes have forced many motorists to reconsider whether paying extra for premium gas is really worth it. Surely if the pump nozzle says "premium" then it's better in every respect than the regular stuff that sells for way less?

Well, the answer is not always clear-cut, and it depends not only on your brand of vehicle but on what type of engine it has, too. So, whether you drive a Mazda, Mercedes, or a McLaren, read on to find out whether Premium gas is really the premium option.

Note

All vehicle data is from reputable sources. Pricing excludes destination charges and tax unless otherwise specified.

What's The Difference Between Regular and Premium Gasoline?

Every gasoline engine works by igniting a mixture of fuel and air. This is how a basic gas-powered internal combustion engine works: The intake valves allow air to enter a combustion chamber, and fuel injectors spray fuel in at the same time. A cylinder then compresses this mixture, and a spark plug ignites it. The resultant explosion forces the cylinder up, creating power. The exhaust valves expel the burnt air and fuel, and the cylinder moves down to repeat the process.

The more air and fuel that can be squeezed into the combustion chamber, the more power the engine makes. Factors such as engine size, valvetrain layout, and the maximum revolutions per minute all have a bearing on how much air and fuel can be effectively used for each engine revolution. While pushing more air into an engine requires larger cylinders and/or forced induction, fuel volume is increased by using larger injectors and more advanced injector spray technology.

The quality of the fuel is also very important, and this is where the difference between regular and premium gasoline comes into play. Fuel quality is primarily measured using something called an octane rating. This rating is the measure of how stable a fuel is. Regardless of whether you see regular, mid-grade, premium, or super premium on the pump, it always refers to the octane rating.

The stability of a fuel determines how it performs under pressure. As the engine revs increase, heat in and around the engine rises as well. At a certain point, the air/fuel mixture may ignite too early, causing "knocking". This can severely damage the engine if left unchecked. Thankfully, modern engines have knock sensors that retard the ignition timing, lowering the combustion chamber pressure and preventing pre-ignition. Unfortunately, this has the side effect of reducing power.

What Benefits Does Premium Gas Provide?

In very simplified terms, premium gas is more stable under pressure than regular gas. This means that it can handle higher heat and pressure, allowing it to remain stable under extreme conditions. The engine control unit (ECU) won't need to retard the timing, and the engine will perform at its peak, even when pushed.

Based solely on this information, you could logically conclude that the higher the octane rating, the more power your car will make. Racing fuels, like the ones developed by Sunoco, have octane ratings ranging from 98 to 118, allowing engines to operate in extreme conditions for extended periods without needing to pull back timing or reduce turbocharger boost levels. But, like chocolate cake, the benefits don't keep stacking up indefinitely, and there are a few mechanical factors that will determine just how effective a higher octane fuel is for your vehicle.

Sources: eia.gov, fueleconomy.gov, gasprices.aaa, Mazda, Toyota

Read the full article on CarBuzz

This article originally appeared on CarBuzz and is republished here with permission.