On the whole, hybrid drivers tend to be pretty attentive to the driving habits that can help them squeeze as many miles per gallon out of their cars’ official EPA ratings as possible. Now, a new study suggests that all car owners should take care follow to proper eco-driving practices, and that failing to do so can hurt a vehicle’s average fuel economy by as much as 45 percent.

According to researchers at the University of Michigan’s Transportation Research Institute, factors ranging from tire inflation to road selection can add up to transform even the most fuel-efficient gas cars into guzzlers. For instance, the owner of an EPA-rated 30-mpg vehicle with poor eco-driving practices could see his average fuel economy drop to as low as 17 mpg if he failed to hit a single point on the study’s checklist—equal to the combined rating of a 2011 Land Rover.

Report authors Michael Sivak and Brandon Schoettle divided these poor efficiency habits into three categories: Strategic decisions, which included engine tuning, tire rolling resistance, tire pressure, and motor oil use; tactical decisions, which included route selection, road grade profile, traffic congestion and load weight; and operational decisions, which included idling, speed, aggressive driving, and cruise control and air conditioner use. Of these factors, route selection, speed, and engine tuning demonstrate the highest potential to sap fuel economy.

The study noted that real-world fuel economy in the United States is just 17.4 mpg, and has risen a paltry 3.4 mpg since 1923. The government-mandated Corporate Average Fuel Economy for cars was 27.5 mpg last year, but those numbers are determined by EPA testing—not by the real-world experiences of drivers. Sivak and Schoettle also point out that perhaps the most profound factor in the stagnancy of automotive transportation efficiency is vehicle occupancy. Since 1960, vehicle occupancy in the United States has fallen 30 percent, causing the average energy intensity of driving to rise by about 30 percent in turn.

Does the Answer Lie in the Center Console?

So if the simplest, most cost-effective ways to increase fuel economy sit not in the hands of manufactures but drivers themselves, how can we coax car owners to do the right thing? Much of the answer can come from the advanced computer systems being installed in many common vehicle models today. These high-tech center consoles were developed in part to help hybrid and electric vehicle drivers monitor their fuel economy and state of battery charge, and have been integrated with GPS navigation and “infotainment” systems to radically alter the driving experience.

Factors like route selection and driving aggression can already be optimized using systems currently found in most hybrids—some of which coach users on the best ways to improve fuel economy as they drive. Computer monitoring of maintenance issues like tire pressure and engine tuning could also help to lead car owners to better eco-driving habits.

While which car you drive can make all the difference in the world, it certainly isn’t the only factor in determining fuel economy. In theory, a combination of good car maintenance, smart driving and carpooling can be just as powerful a fuel-saver as buying a green car. So why not just do both?