What Is Unleaded Gas?

Unleaded gasoline is a type of fuel with no lead additives. It’s better for your health and better for the health of your vehicle.
Written by Andrea Barrett
Reviewed by Jessica Barrett
Unleaded gasoline is a fuel that has no lead additives. Lead exposure can be toxic to your health, but it also leaves harmful residues in your vehicle’s engine that impair performance and could damage your engine. 
Does the type of gasoline you put in your car really matter? It’s an age-old question that many vehicle owners have, and the answer is yes, it does matter. 
When you pull up to the gas pump, you’ll generally have a choice between two types of fuel: regular unleaded and premium. The former is typically cheaper, while the latter can be substantially more. But have you ever wondered what the difference is, other than price? Does one enhance engine performance, or is it all just a gimmick?
Deciphering what’s true and bogus can be challenging, with all sorts of information floating around. Lucky for you,
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What is unleaded gas?

Unleaded gasoline is just as the name suggests—gasoline with no lead added. It was introduced in the 1970s as an alternative to leaded gasoline, which harms the environment and human health. 
But why lead in the first place?
Lead was initially used in gasoline to increase the octane rating, or the fuel’s ability to resist “knocking” or “pinging” during combustion. But while lead may prevent knocking, it can be incredibly harmful to human health. We’re talking about neurological and kidney damage, reproductive issues, and more. Not to mention it’s horrible for the environment. 
Leaded gasoline has been largely phased out in most countries. Some older vehicles still require it, but automotive makers no longer produce cars that need leaded gasoline. 

Regular gas vs. premium gas

When you go to the gas station, you'll see two types of gasoline: regular unleaded and premium. Apart from the serious price difference, what’s the difference between them?
For starters, regular unleaded gas is the most common gas used worldwide. It’s a byproduct of crude oil with high flammability. Premium gas, on the other hand, is referred to as “high octane gas” due to its higher octane number; it’s an unleaded crude oil byproduct but contains detergent additives for better engine performance and less environmental pollution.

Octane rating

When you fill your car, you may notice three numbers indicating the octane rating of each type of gas. Regular is generally 87, mid-grade is 89, and premium is 91 or 93—but what do these mean?
The internal combustion engine of a vehicle compresses a mix of gasoline and air in order to ignite the spark plug and create a controlled explosion. When this explosion happens, it gives your car engine the power necessary to run. 
However, if the fuel mixture ignites prematurely, it creates an unstable explosion; pre-ignition can cause the “engine knock” noise you can sometimes hear. Older cars are more prone to pre-ignition, which usually results in reduced vehicle performance. Over time, it can lead to engine damage. 
This is where that octane rating comes into the picture. The octane rating measures how well the fuel mixture can resist pre-ignition; the higher the rating, the better the resistance. Modern cars contain sensors to detect the issue, so it’s not as big of a problem as in older cars. That’s why most vehicles can use regular or premium fuel. 


The most notable difference between regular and premium gas is the price. Higher octane ratings mean a higher price and depending on your location, the difference can be upwards of 20 cents per gallon. For frequent drivers, high fuel prices can add up to hundreds, if not thousands, of extra dollars each year on gasoline. 
For example, the current average prices for gasoline in California are:
  • Regular unleaded: $5.798/gallon
  • Mid-grade: $5.952/gallon
  • Premium: $6.119/gallon
As you can see, the price difference between regular and premium is $0.321/gallon—multiply that by the number of times you fill up, and your wallet could really be hurting! 
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Why does the octane level matter?

Octane rating is important because it influences the compression of the fuel. A higher octane rating means the fuel can withstand more compression before detonating. Because detonation can result in engine damage, engines are designed to run on a specific octane rating. Although engines designed for premium gasoline can run on regular unleaded fuel, they aren’t as efficient, and power often suffers. 
For most new cars, however, octane level doesn’t make a huge difference, as they can run almost equally efficiently on either. Certain cars do, however, require premium gasoline; your vehicle’s owner's manual will specify which octane fuel your car needs. If there is no information about fuel type, 87-octane fuel (regular unleaded) is what you should use.
For older vehicles, octane ratings were significantly more important, as lower octane fuel could result in engine damage. However, newer cars are built to retune the engine and avoid early ignition with lower octane gas.
That said, just because your vehicle doesn’t require premium gas doesn’t mean you shouldn’t use it. 
In some vehicles, lower octane fuel can reduce your vehicle’s power and fuel efficiency, and it has the potential to lead to engine damage down the line. Plus, some cars may achieve better fuel economy, fewer emissions, and better performance with higher octane fuel. 

Choosing the right fuel for your car

So, what kind of fuel is right for your vehicle? There are a few ways to determine this:

Look at your owner’s manual

Flip to the index of your car manual and look for fuel requirements. The manufacturer usually specifies the recommended fuel, although their recommendations aren’t exclusive unless otherwise stated. You can also find this information online through a quick Google search. 

Check your gas cap

If you don’t have an owner’s manual and can’t find the information online, you may be able to find this information on the fuel door or gas tank cap—it should have a sticker that lists the preferred fuel type for that vehicle. 

Where are you driving?

There are certain times when using premium fuel is advised. For example, your vehicle may perform better with premium fuel when driving through rough terrain or hauling heavy cargo.

How to find cheap car insurance to protect your ride

Although gas prices may be sky-high across the United States, and using premium fuel may get you better gas mileage, you don’t have to spend an arm and a leg to drive your vehicle. If there’s one place you can save, it’s on car insurance—especially when you shop with
As a licensed insurance broker app, Jerry connects you with the best rates from over 50 top insurance providers in under a minute. Whether you’re looking for the most comprehensive
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But the best part? The average Jerry user saves over $800 a year on car insurance—imagine how much fuel you can buy with those savings?! 
saved me $100 a month! They canceled my current policy (even getting me a refund) and switched me to Progressive. All very simple and easy!” —Tara Y.
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Leaded gas was phased out of use in the 1970s in favor of leaded gas. Although more expensive than leaded fuel, regular unleaded gasoline is more environmentally friendly and better for your health.
Yes—as of 1996, all gasoline in the United States and most of the world is unleaded.
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