Car mileage dropping suddenly? These everyday habits may be the reason

Your car’s mileage does not fall only because of engine trouble. Low tyre pressure, heavy AC use, idling, extra weight and fuel-related issues can slowly increase consumption without any dramatic warning sign.

Under-inflated tyres create more rolling resistance, so the engine works harder. The U.S. Department of Energy says properly inflated tyres can improve mileage by 0.6% on average and up to 3% in some cases.

Even a small pressure drop adds up. DOE-backed fuel-saving guidance says under-inflated tyres can lower mileage by about 0.2% for every 1 PSI drop in the average pressure of all four tyres.

AC comfort has a fuel cost. The U.S. Department of Energy says idling can use about a quarter to half a gallon of fuel per hour, depending on engine size and AC use. In city traffic, that extra load is felt more.

Fuel quality can also affect performance. In India, concern around adulteration and ethanol-blended petrol has recently increased, with officials asking states to act strictly against adulteration and supply-chain lapses.

Many drivers keep the engine running at signals, parking spots or outside schools. But long idling wastes fuel without moving the car. Turning off the engine during long stops can help reduce unnecessary consumption.

India’s Oil Ministry has acknowledged that E20 petrol may reduce fuel economy by 3–5% in some vehicles, while saying the broader benefits outweigh the impact. Owners should check vehicle compatibility and official guidance.