As gasoline prices continue to stress household budgets, some drivers are using extreme measures to boost their fuel economy, while putting their lives in danger. Hypermiling—reckless driving techniques that dangerously, and sometimes illegally, stretch a vehicle’s miles-per-gallon (mpg)—includes practices such as rolling through stop signs, driving at erratic and unsafe speeds, tailgating behind large vehicles such as 18-wheelers and putting the car in neutral or shutting off the engine to coast along a roadway.

AAA advises motorists to put safety first. “The goals of hypermiling are positive, such as eliminating aggressive driving and saving energy,” said Marshall L. Doner, AAA Automotive vice president. “Unfortunately, some drivers have taken their desire to improve fuel economy to extremes with techniques that put themselves, as well as their fellow motorists, in danger.”

Additionally, some car owners are making extreme changes in how they maintain their vehicle. For example, some drivers are using the lowest ‘weight’ motor oil available for their vehicle; however, motor oil is not a fluid that can be freely interchanged and using too light an oil could cause major damage to the engine. Instead, AAA advises that drivers follow the vehicle manufacturer’s recommendations as listed in the owner’s manual.

Also, some car owners are dangerously over-inflating their vehicle’s tires, wrongly believing that it will improve their vehicle’s fuel efficiency. Instead, over-inflated tires cause premature wear to the center portion of the tread and make tires more susceptible to road-hazard damage, according to the Rubber Manufacturers Association.

Instead, drivers should properly inflate tires to the pressure specified by the manufacturer in their vehicle’s owner’s manual. This can improve fuel economy by two to three percent, according to the U.S. Department of Energy.

Not all hypermiling techniques are dangerous. Some of the driving techniques that AAA does encourage include: slowing down well in advance when approaching a red light or stopped traffic; gently accelerating and braking; maintaining a steady speed; using cruise control; reducing the weight of the car by removing heavy items; using open windows in stop-and-go traffic, instead of air conditioning; and looking ahead to anticipate traffic changes.