Few vehicles specifically require premium gas. Most vehicles do fine on regular unleaded gas. The cars that do require premium gas are often luxury or high-performance models. If you're wondering whether your car needs premium vs regular gas, the first thing to do is to check your owner's manual.
What Is Premium Gas?
Most likely at some point in your car-driving life you've looked at the row of gas pumps at a gas station and asked, is premium gas worth it? Premium gas is usually defined as the two higher octane pumps after regular unleaded. Both cost more than regular unleaded, sometimes as much as 20 cents per gallon more. However, when it comes to premium gas vs. regular, the answer is more complex than a simple yes or no as to whether it's worth the money.
Although some people consider premium gas to be any variety over regular unleaded, it's actually gas rated at 92 or 93 octane. Gas rated at 89 is usually called Plus and 87 is Regular Unleaded.
Simply put, premium gas has higher octane, which allows certain vehicles to gain more energy from using it. Cars with higher compression ratios or turbo or supercharged engines draw in more air during regular operation. However, that extra air needs higher octane fuel to keep the air/fuel mixture from igniting prematurely. Using lower octane gas in these vehicles often causes this premature detonation, which you then hear as knocking and pinging sounds from inside your engine. Knocking isn't exactly harmless either. Over time it can damage your engine.
What Cars Need Premium Gas?
Many cars will run fine on regular gas; those that require premium gas are often luxury or high-performance models. If you're wondering whether your car needs premium gas, the first thing to do is to check your owner's manual. The manual should specify whether your car requires premium gas, recommends premium gas, or if unleaded is all it needs.
If your car does require premium gas, then it's highly recommended you use it (see above for reasons). However, if premium gas is simply recommended but not required for your car, then it's a little trickier. Modern cars are often able to change the engine timing to allow it to use lower octane gas. This means it can operate smoothly on the lower octane fuel without knocking. Therefore, you won't be risking engine damage. On the other hand, using the lower octane and changing the timing likely means a minor drop in performance. You might see less responsive acceleration or possibly even a slight decrease in fuel economy.
What If The Manual Only Mentions Regular Unleaded?
If your manual doesn't indicate that your vehicle needs higher octane fuel, then there's no point in buying it. In some situations, it's possible for higher-octane fuel to correct knocking or pinging that you're hearing in your car that technically requires only regular unleaded. However, that may only be correcting a symptom of a larger problem, and you should have the car checked out by a mechanic. In most situations, using higher octane fuel on a normal compression engine will not give you many tangible benefits; it won't give you more performance and it won't give you better fuel economy.
Some Myths and Near-Myths About Using Premium Gas
Myth 1: Premium gas increases your MPG. As previously mentioned, it's only likely to do that if your car actually requires premium gas. But many modern cars can adjust to accommodate regular gas and you may not lose much MPG at all. If your car takes regular unleaded, it most likely will not see any boost in MPG from using premium gas.
Myth 2: Premium gas has extra additives or detergents. This stems from confusion between premium gas -- which is higher octane fuel -- and Top Tier fuel. Top Tier fuel does have extra detergents to meet the higher standards of certain automakers who don't believe that the EPA standards are high enough for their modern engines. However, premium gas is simply higher octane fuel designed to give high compression engines proper performance.
Myth 3: Your warranty will be voided if you use regular unleaded in a car that requires premium. This is more of a near-myth as it's possible but unlikely for a manufacturer to decide to void your warranty if you cause engine damage to your vehicle by using regular gas when premium is required. However, as previously mentioned, many modern cars can adjust to regular gas. In short, if you're worried about it, you might want to stick with the required octane rating.
Myth 4: Using regular gas in a premium-required car will cause engine damage. Again, it depends. Modern engines can often adjust to using regular gas and most drivers may never notice a difference. If you use regular gas in your premium engine and never hear any knocking or pinging, you're probably fine. However, if you do hear knocking and pinging while using regular gas in a premium engine, then you can take it as a precursor to engine damage.
What Is Pinging and Knocking and What Causes It?
Pinging and knocking are sounds that come from a car's engine, and they indicate that your fuel/air mixture is igniting early. The result of the knocking is that your car's engine performance will become less efficient, and it can eventually cause serious damage to your engine. So what exactly is happening in your engine to create the knocking? As the piston moves up in the chamber to compress the air and fuel mixture, it receives pressure from properly ignited fuel, which causes it to descend very quickly, which then causes the crankshaft to turn. In the case of a high compression engine burning lower octane fuel, the mixture ignites early. This causes the spark plug fire to collide with the pre-ignition fire; the resulting force hits the piston and creates the ping or knock. If you hear a louder sound, more akin to a knock than a ping, then that indicates a larger unwanted flame during the process.
How Do Knock Sensors Work?
Most cars built later than 1996 have these sensors. The sensor actually hears the pinging or knocking sound and then relays the information to the rest of the system. The system then delays the spark timing to keep the unwanted flame from happening. This usually allows you to use lower octane fuel if you choose to in your higher performance engine.