What are the hidden functions on the fuel tank cap?

2024-08-29

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The Car Fuel Cap: A Hidden Gem of Information and Features The fuel cap is something we must open every time we refuel, but very few people actually pay attention to it. In fact, the fuel cap contains a lot of crucial information that is essential for the correct use of your vehicle. So, what kind of information is included on the fuel cap, and what practical hidden features does it have? Today, we'll uncover some of these hidden functions, hoping to help you better understand and use your car. 1. Drain Hole Inside the Fuel Cap Most cars have several drain holes on the exterior, which are fairly well-known, such as the sunroof drain hole we’ve discussed before. But did you know that there’s also a drain hole inside the fuel cap? This drain hole is designed to prevent water from getting into the fuel tank. When it rains, water can seep through the gap in the fuel cap. Without a small drain hole to remove this water, it could eventually seep into the fuel tank, causing engine failure. During routine maintenance, it's important to regularly clean the drain hole inside the fuel cap to prevent it from being blocked by debris, which could otherwise lead to engine damage due to fuel contamination. 2. Designated Placement for the Fuel Cap During Refueling When refueling, we need to unscrew the fuel cap from the filler neck. But where should the unscrewed cap go? Should we let it hang freely, or place it somewhere specific? If we let the fuel cap hang freely, it can collect dust from the car's exterior, and it might even scratch or corrode the paintwork. To address this, manufacturers have already considered a solution during the car's design process. Typically, there’s a designated slot or hook on the outer cover of the fuel filler area, specifically for placing the unscrewed fuel cap. 3. Determine the Fuel Cap’s Position from the Dashboard Some cars have their fuel caps on the right, while others have them on the left. When refueling, it's essential to park the car on the correct side. But how can you quickly determine the position of the fuel cap from inside the car? Here's a quick tip: Just look at the fuel gauge on the dashboard. There’s usually an arrow pointing in the direction of the fuel cap. Whichever side the arrow points to is where the fuel cap is located. Generally speaking, German cars have the fuel cap on the right, while Japanese cars have it on the left. However, do note that some models might not have this arrow on the dashboard. 4. Emergency Release Lever for the Fuel Cap If, for some reason, the fuel cap doesn’t open normally, you can use the emergency release lever to open it. The emergency release lever for the fuel cap is usually located inside the trunk, near the fuel tank. Simply pry open the panel near the fuel cap with a screwdriver, and you'll find a pull ring inside. Gently pull it, and the fuel cap will open. While this hidden feature is effective, it’s only intended for temporary emergency use. If your fuel cap doesn’t open, it's advisable to visit a service center or repair shop as soon as possible, as relying on the emergency release lever for every refuel can be inconvenient. 5. Fuel Octane Rating Indicated on the Fuel Cap Some new drivers might wonder whether their car requires 92 or 95 octane gasoline. Others may like to "pamper" or "economize" on their car by using higher or lower octane fuel than recommended. However, both practices are incorrect. Simply put, 95 octane fuel has a higher anti-knock quality than 92 octane fuel. Besides this, the proportion of catalytic gasoline, reformed gasoline, and anti-knock agents differs between the two, but overall, there’s no difference in gasoline quality or cleanliness—it's just that they are suited to different engine compression ratios. Therefore, the manufacturer has already determined the appropriate fuel octane rating based on the vehicle's technical parameters and testing before it leaves the factory. Just follow the octane rating indicated on the fuel cap and refuel accordingly—there’s no need to opt for a higher octane rating. 6. Tire Pressure Indicated on the Fuel Cap Tire pressure is extremely important. According to research by Wuhan University of Automotive Technology, incorrect tire pressure—either too high or too low—can lead to tire blowouts. Tire life decreases by 30% for every 20% drop below the standard pressure. On the other hand, overinflated tires are more susceptible to mechanical damage as they lose their flexibility. Every vehicle has its own recommended tire pressure, and you can easily find it indicated on the fuel cap. The markings on the fuel cap specify tire pressure based on the number of passengers and the load in the trunk, allowing you to adjust the tire pressure according to your vehicle's load.