Read About 8 Things That Can Hurt Your Car’s Fuel Economy Here

Everyone keeps a track of their vehicle’s fuel economy. Due to the excessive variations in fuel prices, fuel economy has become a serious matter for car owners. Fuel economy has even changed the buying behavior of customers. The influx of reconditioned Japanese vehicles gained momentum because of their impressive fuel economy as compared to the local vehicles. Fuel economy is not something that is ever green. There are numerous factors that can severely affect the fuel economy of your car. Let’s discuss some of them:

1. Worn out piston rings

Poor fuel economy can be a cause of worn out piston rings probably if you are driving a car with high mileage. High mileage can be termed as 100,000 km for engines up to 1000cc and 170,000 km for engines above 1000cc depending on the condition of the engine. Worn out piston rings and valves results in gradual loss in engine compression which affects the fuel economy and efficiency of the engine. A simple compression test would authenticate the exact condition of your engine.

2. Choked air intake system

Clogged air filter and choked throttle body does not allow the air to pass through freely and does not let the engine breathe properly. Replacing the clogged air filter and getting your throttle body cleaned will not only improve your fuel economy but will also improve the performance of your car. You will feel improvement in the throttle response of your car.

3. Bad Oxygen Sensor

Bad oxygen sensor has one of the most detrimental effects on the fuel economy. Fuel efficiency losses of up to 40%; this occurs when the oxygen sensor is damaged or has malfunctioned. When sensor gets old, worn and does not output appropriate voltages it results in affecting the fuel economy. The oxygen sensor in your vehicle outputs a voltage to your car’s software based on the amount of oxygen in your exhaust. If the O2 sensor is malfunctioning, it will give bogus alerts to ECU and can cause your system to dump more fuel into your air fuel mixture, wasting excess petrol and destroying your fuel economy. You can read more about EFI systems here.

4. Spark plugs

Bad spark plugs can decrease fuel economy by 30%, according some experts. The main cause due to which it consumes more fuel is misfiring of spark plugs so it is highly recommended to replace spark plugs as to ensure better fuel economy. Moreover, Carbon in spark plugs results in lack of current which can also affect the fuel economy of an engine.

Also Read: All You Need To Know About Spark Plugs

5. Bad fuel injectors

Bad fuel injectors also play their hand in affecting the fuel economy; clogging of fuel injectors is one of the most common issue. The metal screen filter inside the fuel injector becomes clogged with dirt particles that are not filtered through the fuel filter, and causes the fuel injectors to flow less fuel than others. This imbalance of proper fuel flow causes the vehicle’s ECU to adjust by adding more fuel into the system and this ultimately lowers the fuel economy. Service them, or replace them if service hasn’t cleared them, to improve your fuel economy.

6. Vigorous acceleration

Vigorous acceleration or bad driving habits is another cause of falling fuel economy. Speeding up gradually saves fuel as compared to accelerating harshly. You can even keep a track of your accelerating habits by monitoring the ECO light in your car’s dashboard, provided your car is equipped with one. Automotive engineers and manufacturers claim that driving your car on ECO mode can help improve the fuel economy up to 15% which is a considerable figure. The ECO check light is more common in Japanese vehicles.

7. Usage of inappropriate motor oil

Many people do not consider the motor oil and use inappropriate motor oil in their cars which results in decreased fuel economy. It is very important to know that all motor oils are not compatible with every type of engine. One should always consider the climate and engine mileage before selecting a motor oil for the engine. For further guidance on engine oils you can refer to one of our articles (Here’s how to know which oil is right for your car).

8. Alignment of Tires

Though it is not a highly contributing factor in decreasing fuel economy but improper alignment of tires can cause fuel efficiency by 8-10%; while on the other hand it causes the tires to wear out rapidly. Uneven tires that are out of balance create vibration in the steering wheel and it forces the engine to decompose more fuel. You can read more about wheel alignment here.

We hope this little piece will help you diagnose any fuel economy issue, if your car is suffering one. Happy motoring!

Shaf Younus

I'm an Auto Enthusiast, a Computer Science Graduate and above all, Citizen of Pakistan.

  • Abdul Hannan

    first thing to check is tyre pressure and size of tyre……and last thing is binding breaks of car

  • Atif

    One other thing you forgot to mention is obsolete and inefficient engine technology.

    Such as with PAKSUZUKI’s lineup, Mehran, Bolan, Ravi, Cultus (early 1980s technology) and Swift (early 2000 technology) as well. While initial cost of PAKSUZUKI vehicles may be low, they are fuel guzzlers. To date no Paksuzuki based vehicle offers VVT in its engines.

    Cars with Variable Valve Timing based system (VVT, IVTEC, VVL, VVLE, VCT etc.) have more efficient engines than older or simpler engines without this feature.

    You can compare a Mehran 0.8 L with City 1.3 MT or Vitz 1.0 L….worst fuel efficiency is of Mehran

    ending note – Engines based on older technology are less efficient.

  • Zulfiqar Ali Soomro

    Bhai vitz ki efficiency marti hai.. and mehran euro 2 has an excellent efficiency and so does cultus..

  • Salman Ahmad

    well said zulfiqar bro.efficiency of mehran euro 2 is much better than previous one.

  • Zulfiqar Ali Soomro

    Yeah.. and Swift has the worst efficiency even that from Sedans.. Corolla is a winner.. although not a fan of any of them but credit should be given where due

  • Salman Hasan

    not sure if 1.3 city can be less thirsty than Mehran 0.8 liter. Where did u get the figures?

  • Junaid

    I have swift that is giving me 140 Km/cylinder with AC in city and 170 km/cylinder on high way and on petrol 11-12km/liter in city and 15km/liter on high way!

  • Zulfiqar Ali Soomro

    Ur one lucky owner then :p

  • Muhammad Adeel

    Well it seems not ok with me, I have Toyota Sprinter model 1986 with its original 1300cc 12 Valve SOHC 2E engine. It gives me 14KM on highway+Karachi City with A/C and 12KM on Karachi City with A/C. The car has all original equipment as came from Japan in 1993. What is the reason behind that? Please answer my query

  • Ahmed Amin Malik

    Bhai, Mehran Euro II will bleed out your City 1.3 MT. I own both, a Euro II and a GLi MT 1.3 and tell you what, GLi doesn’t even come close to whopping 16-18 KM/ Litre city average of Mehran. Keep hating Mehran but call spade a spade.

  • Muhammad Ahmad Habib Qureshi


  • Ali Kamran

    I completely agree with author…. A very good informative article……..
    And @ city 1.3 L is more thirsty than a mehran euro II…….. I own a city 1.3 L MT (2014) and regarding the fuel economy of city……. I completely depends on your driving habits / style. I have achieved 24 kml on highway @ 110 kmhr with AC and within city its average varies from 8-28 kml depending on how you are driving. I have achieved both figures of 8 and 28 kml but first was when I was doing 130 kmh in 3rd gear with AC and second at 60 kmhr in 5th gear with AC. Have you gays ever heard of the term ‘hyper milling’.