From my personal driving experience, I realized that the points below can make your car thirstier than normal.

Dirty/clogged air filter - Clean air filter is needed for proper operation of the car. The air filter does pretty good work for the engine. It does not only clean the air entering the engine, it also avoid debris from making its way to the engine and causing damage. You can easily know a bad air filter by visual inspection. You can as well notice you have a bad air filter when a 'coughing' or 'spitting' noise comes out from your car when stopped in traffic. It indicates that your engine isn't getting enough air as required. Have the air-filter dusted or even replaced when bad.

Under-inflated tires - When your tires are under-inflated, it tends to consume fuel the more. When the pressures are too low, the rolling resistance will impose more load on the transmission thereby making the engine to work harder. Make sure your tire pressure uses the recommended pressure. Bear in mind that some of these roadside mechanics don't give you correct measurement of the tire pressure

Blowing exhaust system - We all know, or at least have been told that a hole in the exhaust system is a bad thing. It will reduce performance, increase CO2 emission. Depending on how bad the leak is, it reduces the power output which will make you go hard on the throttle than you normally do before the blow. This takes more fuel.

http://www.gistalive.com/2015/06/these-causes-car-to-start-consuming.html