The thing most likely to waste fuel is how you drive , especially aggressive or inefficient driving habits. Other factors like poor maintenance and extra weight matter too, but bad driving style usually has the biggest day‑to‑day impact.

Quick Scoop

Biggest fuel wasters

  • Rapid acceleration and hard braking burn far more fuel than smooth driving, sometimes cutting fuel economy by around a third at higher speeds.
  • Driving faster than necessary (for example well above 55–65 mph / 90–105 km/h) increases aerodynamic drag and makes the engine work much harder.
  • Long periods of idling use fuel while taking you nowhere; turning off the engine for stops over about a minute usually saves fuel.

Car condition and setup

  • Under‑inflated tyres increase rolling resistance and are specifically highlighted in driving theory resources as a likely cause of unnecessary fuel use.
  • Skipping basic maintenance (plugs, filters, oil, sensors) makes combustion less efficient and can noticeably raise fuel consumption.
  • Carrying lots of unnecessary weight or using roof racks/boxes all the time forces the engine to work harder and often wastes fuel on every trip.

Everyday habits to fix

  • Many short trips with a cold engine use more fuel than combining errands into one longer journey, because engines run richer while warming up.
  • Running air conditioning on maximum all the time, especially in city driving, adds extra load and can significantly reduce mileage.
  • Constant speed changes on highways instead of using cruise control leads to extra fuel burn compared with holding a steady pace.

In practice, the single “most likely” waste for most drivers is aggressive, stop‑start driving, with tyre pressure and idling close behind.

Information gathered from public forums or data available on the internet and portrayed here.