Does It Matter Where You Get Gas?

Gas is expensive, so you want to get the best bang for your buck, but you don't want to hurt your car. So, it's important to know whether there is a significant difference between brands of gas, what the differences mean, and whether cheap gas can hurt your car. The quick answer is it's generally fine to use the cheapest gas you can get. However, there are differences between brands of gas and there are consequences from using cheap gas.

All Gas Is the Same (Up to a Point)

If you ever get the chance to see a pipeline carrying petroleum, you'll see it bears logos from multiple companies. Once the petroleum gets to the refinery, it is made into gasoline. Oil tankers carry this gas to different companies, so the gasoline part of gas is the same. However, each company is required by law to put additives in the fuel. The composition, quantity, and quality of the additives is proprietary. All gas contains additives, but they aren't created equal. Does it matter? Yes and No.

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Additives Can Matter

While most of gas consists of gasoline, it also contains additives, and usually ethanol. The additives include detergents, which help prevent fuel injector clogs and deposits from forming in the engine. The chemicals are approved by the U.S. Environmental Protection Agency and are required by law. Whether your gas comes from Arco or Exxon, it contains detergent, but cheaper gas tends to contain the minimum amount of additives. Mobil, for example, claims to contain twice the amount of additives compared with generic gas. Studies have shown regular and discount gas both meet octane and detergent criteria and offer correct seasonal formulations. For the most part, the difference between the fuels is that buying discount gas can save you a lot of money at the pump.

However, gas with more additives does a better job at preventing engine wear. If you're driving a rental car or aren't planning on keeping a vehicle long enough that engine performance is a priority, you'll likely consider the more expensive additives a waste of money. If you're looking to maximize your engine's performance and keep it in peak condition as long as possible, you'll probably choose to spend a bit more to get the best fuel for your car that's available. These would be what are called the "Top Tier" fuels and they are clearly marked at the pump at Exxon, Shell, Mobil, Chevron, and other stations. Another option is to buy generic gas and then add fuel injector cleaner yourself. You'll get the benefits of added detergents while saving money over premium brand gas.

Ethanol in Gas

Aside from the difference in the amount and formulation of additives, another big difference between cheap gas and name brand gas has to do with ethanol. Modern automobiles are sophisticated machines, capable of compensating for fuel variations, but increasing the amount of ethanol in gas results in lower fuel economy. If you buy gas containing a lot of ethanol, you won't make it as far between fill-ups, so you may not actually be saving yourself money at the pump. Arco calculates fuel economy is 2-4% lower for their ethanol-containing fuels, for example.

It's hard to avoid ethanol, since even Top Tier fuels almost always contain 10% ethanol. However, some fuels now contain 15% ethanol or more. Check your vehicle handbook, since some manufacturers actually warn against using this fuel, as it's potentially damaging for high compression engines. It's possible to buy ethanol-free gas, but increasingly difficult. Its presence, however, is more likely to affect your fuel line than the amount and type of additives in your gas.

The Bottom Line

For just about everyone, cheap gas means more money in your pocket and little to no chance of harm to your vehicle. If you drive a car where minute difference in fuel formulation matter, you knew this from the outset. You can still pick up a bargain every now and then, but would do better to stick to the gas your baby likes for regular fill-ups.