Why Your Petrol Car’s Mileage Is Dropping – Causes & Solutions

Why Your Petrol Car’s Mileage Is Dropping?

1. Poor Driving Habits

One of the most common causes of low mileage is how you drive. Aggressive driving, sudden acceleration, harsh braking, and idling for long periods all contribute to increased fuel consumption.

Solution:

• Drive smoothly: Gradually accelerate and brake.
• Avoid: frequent idling. Turn off the engine if you’re stopping for more than a minute.
• Use: cruise control on highways to maintain a consistent speed.

2. Underinflated or Worn-out Tyres

Tyres that are underinflated create more rolling resistance, forcing your engine to work harder and burn more fuel. Similarly, worn-out tyres can negatively impact your fuel economy.

Solution:

• Check: your tyre pressure weekly and maintain it as per manufacturer’s specifications.
• Replace: old or worn-out tyres with fuel-efficient radial tyres.

3. Dirty or Clogged Air Filter

Your car’s air filter ensures clean airflow to the engine. When it gets clogged with dirt and dust, the engine struggles to draw in enough air, resulting in poor combustion and reduced mileage.

Solution:

• Inspect and: clean or replace your air filter every 10,000–15,000 km, or more frequently if you drive in dusty conditions.

4. Faulty Oxygen (O2) Sensor

The oxygen sensor monitors the level of oxygen in the exhaust and helps adjust the air-fuel mixture. A faulty sensor can cause the engine to run too rich (too much fuel), resulting in high fuel consumption.

Solution:

• Get: the oxygen sensor checked during routine service.
• Replace: it if needed—this simple fix can improve mileage by up to 40% in some cases.

5. Using Low-quality or Wrong Grade Fuel

Filling your tank with substandard petrol or using a different octane rating than recommended can hurt performance and fuel efficiency.

Solution:

• Always use: trusted fuel stations.
• Follow: your car manufacturer’s recommendation for fuel grade (87, 91, etc.).

6. Engine Oil Quality and Type

Using the wrong engine oil viscosity or old engine oil can cause increased friction in the engine, making it work harder and burn more fuel.

Solution:

• Stick to: manufacturer-recommended engine oil (check your owner’s manual).
• Change: engine oil at regular intervals (usually every 5,000 to 10,000 km).

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7. Fuel Injector Issues

The fuel injectors spray petrol into the combustion chamber in a fine mist. When clogged, they don’t deliver the proper amount of fuel, affecting combustion and reducing mileage.

Solution:

• Add: fuel injector cleaners to your fuel tank occasionally.
• Get: your injectors cleaned professionally if the mileage remains low.

8. Spark Plug Problems

Spark plugs ignite the fuel-air mixture. Old or damaged spark plugs can cause incomplete combustion, leading to wasted fuel and poor engine performance.

Solution:

• Inspect: spark plugs every 20,000–30,000 km.
• Replace: faulty or old spark plugs with high-quality OEM replacements.

9. Excessive Use of Air Conditioning

The AC system puts an extra load on your car’s engine, especially in slow traffic, reducing your fuel efficiency.

Solution:

• Use: AC only when necessary.
• At low speeds: roll down the windows instead of using AC.
• Park: in the shade to reduce cooling time.

10. Carrying Unnecessary Weight

The more weight your car carries, the harder the engine works, especially in city traffic. Even roof racks and carriers add to aerodynamic drag and reduce mileage.

Solution:

• Clear out: the trunk of unused items.
• Remove: roof carriers if not in use.

11. Frequent Short Trips

Short trips prevent the engine from reaching its optimal operating temperature, leading to higher fuel consumption.

Solution:

• Combine: errands to reduce cold starts.
• Walk: or use a two-wheeler for very short distances.

12. Faulty Sensors and Electronics

Modern cars rely heavily on sensors for engine management. Faulty MAP, MAF, or throttle position sensors can disrupt the air-fuel ratio, reducing efficiency.

Solution:

• Get: a diagnostic scan done at a trusted workshop.
• Replace: faulty sensors promptly.

13. Poor Quality Maintenance or Ignoring Servicing

Skipping or delaying car servicing can lead to a build-up of carbon, clogged filters, and deteriorating parts, all of which affect performance and mileage.

Solution:

• Stick to: a routine maintenance schedule.
• Choose: certified workshops for servicing, oil changes, and filter replacements.

14. Low Engine Compression

Engines with poor compression can’t burn fuel efficiently. This is usually a sign of wear and tear in the engine’s internal components and may require an overhaul.

Solution:

• Get: a compression test done.
• If necessary: consult a trusted mechanic for engine repair or reconditioning.

15. Fuel Tank Leaks or Evaporation

If your car is older or has been through rough terrain, check for minor fuel leaks or faulty fuel caps that may cause fuel evaporation.

Solution:

• Inspect: under your vehicle for fuel odours or leaks.
• Replace: a worn-out fuel cap.

Bonus Tip: Use Technology to Monitor Mileage

Use mileage tracking apps or your car’s onboard computer to keep an eye on fuel usage. If you see a sudden dip, it’s a clear sign that something needs attention.

Summary Table – Common Causes vs. Solutions

Problem	Solution
Aggressive driving	Drive smoothly and avoid sudden braking
Underinflated tyres	Maintain proper tyre pressure
Dirty air filter	Clean or replace regularly
Faulty oxygen sensor	Replace after diagnostic check
Wrong fuel	Use the recommended grade from reliable stations
Wrong engine oil	Use the manufacturer-recommended oil
Clogged fuel injectors	Use fuel injector cleaner or get them cleaned
Old spark plugs	Replace with high-quality spark plugs
Overuse of AC	Minimise AC use, especially at low speeds
Extra weight or roof racks	Remove unnecessary load
Short trips	Combine errands
Faulty sensors	Get a diagnostic scan and replace as needed
Skipped servicing	Follow the maintenance schedule
Low engine compression	Check and repair if necessary
Fuel leaks	Inspect the tank and fuel cap

Final Thoughts

A drop in mileage isn’t just a minor annoyance—it’s a warning sign. Ignoring it can lead to costlier repairs down the line and a significant dent in your monthly fuel budget. By identifying the causes and applying the simple solutions shared above, you can restore your petrol car’s mileage, extend its lifespan, and drive more efficiently.If you're not confident in diagnosing the issue on your own, always consult a professional mechanic or service centre. Preventive care is always better than a major repair.

"Stay smart. Drive efficiently. Save fuel."

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