- COLD ENGINES: It needs about 10 to 15 minutes before the car engine is really efficient. So if your car does short 5-minute trip to the market, bank, school, friends, etc., the engine never gets warm enough and fuel consumption may go up by 50%.
- DRIVING AT HIGH ENGINE SPEEDS (High RPM): If you rev up your engine and drive at high speeds in each gear (i.e. drive at high car rpm's in each gear), the fuel would be consumed at a much faster rate. Conversely if you keep the engine at minimum speeds your fuel consumption will be much better but driving in too slow speeds may also cause knocking and shorten engine life.
- DRIVING AT HIGH CAR SPEEDS: The aerodynamic drag on the car increases dramatically the faster you drive. For example, the drag force at 70 mph (113 kph) is about double that at 50 mph (81 kph). So, keeping your speed down can increase your mileage significantly.
- TOO MANY STOPS AND STARTS: Driving in traffic is a fuel consumption killer with idling at red lights or when stuck at traffic. If you spend 10 minutes idling your car on a 30 minute trip, your fuel consumption may double.
- THE WEIGHT OF THE CAR: All modern engines are quite fuel efficient but the weight of the car is a major factor. A 600 kg Maruti 800 weighs half as much as a Corolla that will naturally need more fuel.
- ENGINE TUNING AND TIMING: Most modern engines with MPFI and other electronic engine management systems need very little tuning unlike the old carburetors but the nozzles and injectors do need to be cleaned especially with dirt or adulterated fuel that is sometimes encountered. So get your car serviced regularly by your authorized dealer.
- AIR, OIL AND FUEL FILTERS: Choked filters can play havoc with fuel consumption of a car so ensure that these are regularly serviced and changed when they are dirty or clogged.
The fuel consumption figures under test conditions assume nearly perfect conditions on a flat one km run so do not expect the figures reported in tests to apply in city conditions where it may be out by 25% or more.