If your bike seems to be using more petrol than it used to, the cause is usually one of a short list of things, and most of them are cheap to fix. Before looking for a cause, though, it is...
If your bike seems to be using more petrol than it used to, the cause is usually one of a short list of things, and most of them are cheap to fix. Before looking for a cause, though, it is worth making sure the drop is real. Here is how to measure mileage properly, and the causes the manufacturers themselves list in their owner’s manuals.
The short answer
- Measure it properly first, with the full-tank-to-full-tank method. Dashboard readings are estimates.
- The usual causes: low tyre pressure, a dirty air filter, a worn spark plug, old or low engine oil, dragging brakes and riding habits.
- Your bike will not match its test figure, and the manufacturers say so. On-road mileage depends on road, load, speed and maintenance.
Step 1: measure it properly
Bajaj’s Pulsar 150 manual (page 22) describes the full-tank-to-full-tank method:
- Fill the tank to the brim.
- Ride normally for about 100 km.
- Fill it to the brim again at the same station, ideally from the same pump.
- Divide the kilometres ridden by the litres you just filled.
Do not rely on the dashboard. Bajaj’s manual says its instantaneous and average fuel economy readings are indicative and vary with riding and road conditions, and TVS’s Jupiter 125 manual says the fuel level display is for reference only and should not be used to calculate mileage.
Also keep expectations realistic. TVS’s manual states plainly that on-road mileage depends on road condition, fuel quality, riding speed, braking, tyre inflation, maintenance and load, and will differ from the figure measured under standard test conditions.
Step 2: the maintenance causes
Low tyre pressure
The easiest one to fix. TVS’s manual explains that low tyre pressure increases drag and reduces fuel economy, recommends checking pressure weekly when the tyres are cold, and says a weekly check helps improve tread life and fuel efficiency by 10%. Bajaj’s manual also lists correct tyre pressure for better fuel consumption. The right pressures are in your manual; check them cold, before riding.
A dirty air filter
TVS: a dirty air cleaner element restricts airflow and increases fuel consumption. The Jupiter’s paper filter is replaced every 12,000 km rather than cleaned. Other bikes have different intervals: the Pulsar 150’s is every 15,000 km and the Hunter 350’s every 10,000 km. All of them need it sooner in dusty conditions.
A worn or dirty spark plug
TVS: a dirty or defective spark plug wastes fuel through incomplete combustion. The Jupiter’s plug is replaced every 12,000 km.
Old or low engine oil
TVS: dirty or low engine oil increases friction inside the engine and increases fuel consumption. Use the grade your manual specifies; see which engine oil does your bike need?
Brakes dragging, or a wheel that does not spin freely
Bajaj’s list of maintenance points includes making sure the brakes are not dragging or binding. TVS recommends spinning the wheels by hand about once a week to check they turn freely.
Clutch play, fuel leaks and a stuck choke
- Clutch: Bajaj lists correct clutch lever play among its maintenance points. A clutch that slips wastes power.
- Fuel leaks: both Bajaj and TVS say to check the fuel lines and connections. Any petrol smell around the bike deserves a look.
- Choke: on older carburettor bikes, Royal Enfield’s Classic 350 manual warns that riding with the choke on causes high fuel consumption.
Step 3: fuel and riding habits
- Harsh braking and acceleration. Bajaj advises riding smoothly at a steady speed and using the throttle judiciously. TVS warns never to accelerate and brake at the same time on its scooter, as it wears the clutch shoes and wastes fuel.
- Idling. Bajaj suggests switching the engine off if you will be stopped for more than two minutes.
- Load. Do not carry more than the specified payload.
- Parking in the sun. TVS notes that fuel evaporates from a bike parked in hot sun, and more so with a low tank. Always close the fuel cap properly.
- Fuel. The Jupiter 125 is approved for BS VI petrol with up to 20% ethanol (E20). TVS’s manual notes that higher ethanol content can decrease fuel economy, and suggests trying a different station if you notice problems. Always fill at a reputable station.
When it is time for a service
If the tyre pressure is right, your riding has not changed and the measured mileage is still well down, a service is the next step. Most of the causes above, including the air filter, spark plug, oil, brakes and clutch, are exactly what a proper general service checks. If your bike is overdue, see bike service intervals for when it should have been done.
Our doorstep general service packages are priced by engine size, from up to 110 cc to up to 300 cc. Tyre pressure is checked as part of the service, although tyre replacement and puncture repair are not work we do. If your bike is still under warranty, read does doorstep bike service void your warranty? first.
Sources: TVS Jupiter 125 owner’s manual (pages 32, 69–70 and 88); Bajaj Pulsar 150 owner’s manual (pages 8 and 22); Royal Enfield Classic 350 owner’s manual (page 15). Last updated: 22 September 2026.
