What Happens If I Don’t Use Premium Gas In My Lexus?


What Happens If I Don't Use Premium Gas In My Lexus?

Premium gas costs more than regular gas. Filling your Lexus with premium gas every time might break your bank, especially if you live on a budget. It is understandable if you are tempted to fill with regular gas even when the automaker recommends premium.

Does using premium have an impact on your car’s performance? Will using regular gas damage the engine of your Lexus?

What Happens If I Don’t Use Premium Gas In My Lexus?

If the Lexus model requires premium, it means that the automaker engineered the engine to operate under high octane gas. Using regular gas, which has a lower octane rating, increases the chances of uncontrolled self-combustion, which can lead to engine knocking.

Luckily, not all Lexus cars require premium gas to operate normally. Whether or not to use premium gas depends on what the automaker requires.

But what happens if you still use regular gas when the automaker requires premium gas?

Lexus requires high octane gas for its performance cars, such as the coupes. These cars have high compression engines that can detonate if you use lower octane gas. Luckily, modern computers can tweak the ignition system so that your car runs on regular gas – only up to a point.

If you continue using regular gas, the performance of your car will suffer and so will the fuel economy. Even worse, regular gas makes your car’s engine more prone to detonate.

While you may not note any difference in performance, using regular gas will result in engine knocking. The knocking sound starts slow and then becomes consistent and sometimes annoying. Knocking can lead to damage of the ignition system components such as pistons, spark plugs, and valves.

Modern engines have a knock sensor; they have had one for the past 20 years. The sensor detects detonation in your engine and notifies you. This happens when you use regular fuel.

When the sensor detects detonation, it impedes the spark timing of the engine to ensure the knocking does not damage any parts. But this still doesn’t help your engine.

The sensor impeding your spark timing lowers your engine power, makes the car less drivable, and lowers the gas mileage. However, if the sensor is defecting and engine knocking continues, you end up with a damaged engine.

The bottom line is, if Lexus requires that you use premium gas, or at least octane rating 91, do not use regular gas. If your engine sustains damages from the use of regular gas, you void your warranty. This means you will have to pay for the damages, which can be more than the coins you save buying regular gas.

How Does Engine Knock Occur?

Engine knock results from self-combustion of gas air mixture in an unburned region. How does this happen?

Combustion happens when vaporized gas mixes with air inside the combustion chamber. The rising pistons will compress the mixture and the spark plug will fire to start the combustion process. Combustion is not instantaneous, however.

The flame kernel develops slowly, grows, and then slowly burns the contents of the combustion chamber. There is the mixture in the burning region and some in the unburned region. At some point during the combustion process, the mixture in the unburned region might be heated by the burned gas as the pistons compress it.

The heated mixture in the unburned region can self-combust in an uncontrolled manner, and this is how knocking occurs. This knocking or pinging can damage the engine. High octane gas compresses and heats to a greater degree and does not self-ignite, and this is why high performance cars require premium gas.

Which Lexus Models Require Premium Gas?

On some models, Lexus “Recommends” the use of premium fuel. If this is the case, you can use regular gas without any damages on your engine. Using premium gas will slightly improve performance and gas mileage of your car, but you may not even notice the difference.

On other models, Lexus “Requires” that you use premium gas. These are models whose engines are designed to run on high octane gas to operate without detonation. If your Lexus requires premium only, you do not have an option but to use premium gas lest you damage the engine of your car.

Drivers no longer opt for premium gas for its cleanliness and the additives in it. Due to regulations on emissions, even regular gas comes cleaner and with additives that protect your car. As such, unless your car requires high octane gas to perform optimally, you never have to go for premium gas.

Most Lexus models will operate efficiently on regular fuel. For the Lexus SUVs, you can run UX, UX Hybrid, NX Hybrid, and RX on regular fuel without any damages to the engine. These models require a minimum recommended octane rating of 87, which is regular gas.

Other SUVs, including Lexus GX, NX, RX Hybrid, and LX require the use of premium gas. Lexus requires that the minimum gas octane rating be 91, which is premium gas.

All Lexus coupes, which are high performance cars, require high octane premium gas. The engines of these cars run with a high compression ratio to generate more power. Using regular gas will lead to knocking, which results in engine damages.

The automaker recommends the minimum octane rating for these performance cars should be 91.

The Lexus sedans require either premium or regular gas. Those that run smoothly with regular gas include Lexus ES and EX Hybrid. These two require an octane rating of at least 87.

The Lexus IS, Lexus GS, LS, and LS Hybrid require premium gas with an octane rating of at least 91.For these models, using regular gas will damage the engine.

If My Lexus Recommends Premium Gas, Can I Use Regular Gas?

Yes. You will have no problem using regular gas. Most automakers recommend regular gas for drivers who need better performance.

Unless the automaker requires that you only use premium gas, using regular will not harm your car’s engine. Premium gas contains higher octane rating, which prevents knocking or pinging. The premium fuel can have a rating of the 90, 91, or 94 or higher octane.

The higher octane rating is what makes the fuel more expensive. Fuel refineries add alkylate into the fuel, an expensive substance that works well with engines with a high compression ratio. A few years ago, engines did not have the features to deal with fuel of varying octane levels.

What Happens If I Don't Use Premium Gas In My Lexus? If My Lexus Recommends Premium Gas, Can I Use Regular Gas?

Using the wrong fuel on performance cars would result in instant damages to the engine parts. Today, engines have more advanced controls that can adjust ignition timing to ensure that pinging does not occur. The ability to adjust tunes engines and gives drivers more flexibility in the fuel they use.

Low octane gas doesn’t allow ignition advance when you need rapid acceleration. If a high performance car needs more ignition advance, the spark plug fires sooner, and this is how they generate more power and drive quickly.

In cars that use low octane gas, the spark plug doesn’t fire sooner, and this results in lower acceleration. You will note the loss in power more if your car has a turbocharged gasoline engine. These engines are very common in performance cars. If you only accelerate moderately, you will not see any change in performance.

Is Premium Gas Better for the Cleanliness of My Engine?

You can tell if your car needs premium fuel by looking at its user manual. The manual shows the minimum octane rating that your car requires for optimal operation and to reduce knocking. If your car doesn’t require premium fuel, using it will not have any effects on your engine’s cleanliness.

Using premium gas doesn’t prevent engine deposits, doesn’t remove the deposits, and does not clean your vehicle engine any more than the regular gas. Today, regulations on fuel refinery have made sure that fuel of any octane grade is safe for your engine and for the environment.

The EPA requires that all gasoline brands and grades contain engine cleaning additives that clean your engine and protect against the buildup of engine deposits. This way, whether you use premium or regular gas, your engine will be safe from deposits.

You should only switch if your car knocks. There are some engines that will still knock even if you use fuel with the recommended octane rating. In such a case, switch to higher octane rating and see how it goes.

If pinging continues even after using high-grade fuel, you may need to take your Lexus for repairs or any other tune up. After the tune up, you can shift to the minimum recommended octane rating for your car.

How is Fuel Labeled at the Gas Station?

The fuel pump has a yellow sticker that shows the octane rating of the fuel the station sells you. Note that premium gas doesn’t have the same rating across the country. In some states, the minimum octane rating for premium gas is 92 while in other states, the minimum rating for premium gas is 90.

The yellow octane sticker on the gas pump will show you what is premium in your state. This sticker should match with the minimum recommended octane rating for your Lexus. Most Lexus models require either regular at an octane rating of 87 or premium at a rating of 91.

If you do not see the octane rating of gas on the fuel pump, you can file a complaint with the Federal Trade Commission. The FTC ensures that the marketers and gas station owners give you the information you need.

Closing Thoughts

As a rule of thumb, avoid using fuel whose octane rating is below the minimum recommended by the automaker. You can see the recommended octane rating of your Lexus GX or any other on the user manual of your Lexus.

Lexus is a luxury brand and most of their vehicles have specific requirements. Using regular gas on a car that needs a minimum octane rating of 91 might lead to knocking and engine damages. Although modern engines have more advanced controls, it is still not safe to use lower octane rating fuel if you need to keep your warranty alive and protect your Lexus engine.

John Nelson

You can find John stringing a hammock from the back of his SUV to a tree camping in the outdoors most weekends during warmer weather. John loves the outdoors and the freedom four-wheel-drive vehicles offer.

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