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Poor Gas Mileage – What Is The Cause?

Poor Gas Mileage

Have you ever brought your car to a gas station to notice that your fuel level has dropped significantly than just a few hours ago? The decline in fuel could be a sign of poor gas mileage and indicate something is wrong in your vehicle, leading to a lower fuel economy and reduced efficiency. 

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Determining the top causes of poor gas mileage and the main symptoms can prevent this issue from lingering in your car. Let’s see the potential culprits for reduced engine performance and how you can keep these problems from worsening over time. Preventing poor gas mileage is crucial to keeping your car running at a high level!

Top Causes of Poor Gas Mileage

As cars age, there might be numerous reasons why your fuel consumption is much higher than usual. You might be wondering why this is happening, and what has caused this poor gas mileage to occur suddenly. Why is your car burning gas so fast? Why do you frequently have to fill up your gas tank? Keep reading to figure out the top reasons for poor gas mileage.


  • Carbon Buildup


As your car gets older and succumbs to more wear and tear, contaminants, debris, and dirt builds up on various parts. Carbon builds up on the internal mechanisms, like pistons, valves, and cylinder walls, leading to a lack of performance and reduced efficiency. The buildup of any unwanted product on the internal cylinders and pistons reduces the compression necessary in the engine, leading to a lower fuel economy. 


As a driver, you need to be especially aware of this problem if you own a car that uses direct injection in the fuel system. Direct injection transfers fuel into the cylinder without any middle part being used in the process, whereas a port injection transfers the fuel before the intake valve. Since direct injection fuel cylinders are more likely to succumb to carbon buildup, you need to be aware of this as a potential cause of poor gas mileage. 


  • Damaged Piston Rings 


In addition, as the vehicle gets older, the piston rings can break down after substantial use. Since the piston rings seal off the cylinder wall, a damaged piston ring can reduce the system’s compression and cause a lower fuel efficiency. 


The piston rings’ breakdown can be due to worn piston rings, incorrect oil used, and the oil level being consistently low when driving the car. If you are someone who frequently forgets to top up their oil or refills their gas tank when it is low, then you need to keep an eye out for poor gas mileage. 


Furthermore, another cause of damaged piston rings can be consistent lugging on your engine. “Lugging your engine” involves driving your vehicle at full throttle with the engine at low RPM. This process can severely hurt your engine and your car’s performance since the transmission is working in a gear that is too high for the current demands. 


Since the crankshaft drives most oil pumps, if you frequently drive your vehicle at a high load at a low RPM, the oil pump will send an improper amount of oil to the car’s parts that require additional oil. The malfunctioning of the oil pump and the engine lugging can lead to poor gas mileage. To prevent this from happening, you need to downshift before accelerating.


  • Poor Driving Habits 


Although you may need to get to work or school as quickly as possible, frequently accelerating and decelerating at the drop of a hat can wreak havoc on your fuel economy. When you step on the gas, the throttle plate opens and allows extra air to enter the combustion chamber. This process triggers the engine control unit to respond appropriately. This mechanism needs to inject additional fuel to keep the air and fuel ratio right to prevent poor gas mileage.


However, when you consistently drive with aggressive driving habits, you can exacerbate your vehicle’s problems that lead to a reduced fuel economy. If you frequently use more fuel when driving, there will not be enough extra fuel to cool the cylinders and prevent engine knock. 


Engine knocking, also known as pre-detonation or pre-combustion, refers to fuel that ignites before the spark plugs fire. If the spark plugs do not trigger the ignition, the engine has the potential to overheat and potentially explode during use, leading to a very dangerous and hazardous driving condition. 


The solution to this reason for poor gas mileage is using safer and steadier driving habits. By driving a bit slower, producing sudden acceleration, and gunning the gas pedal, you can prevent an unsafe driving condition and reduce the chances of poor gas mileage in your vehicle. 


  • Tailgating


If you frequently drive a little bit too close to the car in front of you, this could be a surprising reason for poor gas mileage. When you tailgate the car, you end up hitting the brakes more frequently than keeping your car safe. To prevent hitting the car in front of you, you must consistently switch between braking and accelerating, instead of just cruising at an average speed. 


Not to mention, tailgating the car in front of you creates traffic and congestion to the cars around you, leading to unsafe driving situations. Instead of following too close, keep a safe distance to reduce the poor gas mileage. 


  • Cold Weather


If you live in a cold climate or frequently drive in cold weather, your car could suffer from poor gas mileage. When the outside air is colder, it takes longer for your vehicle to warm up and reach the proper operating temperature to run efficiently. This reduced fuel efficiency is that the oil becomes more viscous at colder temperatures, reducing the efficiency of the oil in your engine. 


To remedy this problem, you might have to get a little creative to keep your car warmer during the cold-weather winter months. Besides moving to a warmer climate, there aren’t too many solutions. However, if you keep your car outside in a driveway or exposed garage, consider moving your vehicle to an inside garage to reduce poor gas mileage chances. 


  • Using Incorrect Fuel Type


If you do not use the correct fuel prescribed for your vehicle, this can lead to a reduction in fuel economy and create poor gas mileage. Make sure you read the proper octane rating you need for your car to keep it running efficiently. The higher the octane, the better quality the oil is, and the more resistant it is to engine knocking. 


Typically, you will find most cars are okay with using the lower octane oil, generally labeled ‘87 octane.’ However, some vehicles require the middle of the road options, needing 89 octane rating, while luxury vehicles and sports cars typically require 91 or 93 octane gasoline. 


If you go to fill up the tank of your high-end sports car and use 87 octane rating, you might find that the gas mileage will decline. Be sure to double-check your owner’s manual to ensure you are using the correct kind of fuel. 


Using the wrong octane rating fuel means that the spark plug fires at the incorrect time, leading to poor gas mileage. The best solution to this problem is to use the octane fuel required by your specific make, model, and year of your car. 


  • Low Tire Pressure


If your tires do not inflate to the proper level, your vehicle’s fuel efficiency will significantly drop. Low tire pressure increases the tire’s resistance against the road surface, requiring extra energy from the engine. This extra energy places more stress on the engine and leads to poor gas mileage. 


Unfortunately, the main way that the driver notices the low tire pressure is when the tire gets to the point of no return – you need to immediately fill up the air on your tires or stop at an auto body shop to remedy this issue. Driving on tires that are way below the necessary standard can result in damage to the wheels themselves. 


To fix low tire pressure, check your tire pressure regularly using a tire pressure gauge, paying attention to the dashboard warning lights, and feeling for any inconsistencies while driving. Doing these simple tasks can help prevent an expensive wheel replacement and reduce poor gas mileage chances. 


  • Bad Wheel Alignment


Proper wheel alignment ensures your vehicle rolls straight, your tires are not rolling unevenly, and your tires are not fighting against the road’s resistance while driving. If you hit a pothole or an object in the road, you might notice that your car begins to drive unsteadily. In this case, you need to pay for wheel alignment to keep your vehicle safe and reduce poor gas mileage chances. 


  • Use Thinner Oil


Although some old-school car owners and car mechanics might claim that thicker oil helps to reduce the prevalence of leaks and lifter noise, this is a myth that you should not follow. Using thicker oil can create more resistance in the engine, leading to a lower fuel economy and poor gas mileage. Instead of just using the most viscous oil you can find, check the owner’s manual to see what kind of oil works well for your vehicle. 


  • Too Much Oil


As you might tell by now, oil problems are the main cause of poor gas mileage in most vehicles. If you decide to change your oil due to using the incorrect type or having a low oil level, you might end up filling up the tank a little too much. In this case, the oil might harm the crankshaft. 


To prevent filling up your car with too much oil, you might need to buy a fluid extractor or bring your car to a mechanic to reduce the oil level to just below the ‘full’ mark. For future reference, you should always fill up your vehicle’s oil to between the full and empty lines on the dipstick to prevent any crankshaft issues and poor gas mileage. 


  • Damaged Ignition Coils, Spark Plugs, or Wires


The ignition and the fuel system work together in keeping the engine running at a high-performing level. If the spark plug or the ignition coil shows signs of wear and tear, the cylinder might not be able to combust at the proper time. If the cylinder does not receive the right signals, the engine will misfire and lead to poor gas mileage in your vehicle. 


If the cylinder does not combust at the right time, there will be excess fuel just sitting in the tank. Since unburnt fuel can’t be used correctly to power your vehicle, the fuel will go to waste, reducing fuel efficiency. If you notice that your engine has rough idling or is frequently stalling, you should check your ignition system to see the reason for poor gas mileage. 


  • Clogged Fuel Injector


The main function of the fuel injector in your car is to transfer fuel at a specific time and in a certain way. Suppose your fuel injector shows signs of damage and injects fuel at an incorrect interval. In that case, the injector might spray fuel in an erratic pattern, leading to a reduced fuel economy. In this case, you should clean your fuel injector to get rid of any built-up debris, contaminants, or dirt that is causing the poor gas mileage. 


By knowing the top reasons for poor gas mileage, you can quickly and efficiently diagnose your vehicle’s issue. Knowing the main parts to look out for when figuring out the culprit for the reduced fuel efficiency can help you prevent any further damage in your car. This knowledge will make the repair and replacement much easier, quicker, and cheaper. Analyzing the performance of your car, the efficiency of your fuel system and the potential problems in your ignition system can help you reduce the likelihood of poor gas mileage. 

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