The process of maximizing fuel efficiency (also known as hypermiling) has been around for a long time. This practice has recently become more popular with the skyrocketing price of fuel. It is a combination of techniques, that when applied in unison, can drastically increase a vehicle's fuel efficiency.
Maintain Efficient Speed
Driving at an efficient speed is one of the most important factors to increasing fuel efficiency, particularly when driving at a steady speed for any sort of distance. Being able to cruise without stopping/starting, at the lowest throttle possible, while operating in the highest gear possible is the best combination for fuel economy.
Further, every vehicle has an 'optimal speed' at which the vehicle's engine is the most efficient. A general rule is to keep your vehicle's speed between 80-89 km/h., however the exact 'optimal speed' for each vehicle is different. Be sure to research your exact year and model of vehicle to determine the most efficient speed to drive at.
When to Accelerate or Brake
Acceleration and deceleration (braking) are often the largest contributors to fuel consumption. Both the frequency of speed changes, and the manner in which they are done play a large factor in the total fuel economy of the vehicle.
When accelerating, it is best to accelerate at a steady rate until up to a desired speed. Accelerating slowly is less efficient then accelerating at a medium rate to get up to speed. 'Flooring it' however, is also not the most efficient option. Once up to speed, your vehicle is using mostly its momentum and kinetic energy to move, rather than fuel. So it is important to avoid braking if possible in order to maintain that momentum. (NOTE: never sacrifice safety for fuel economy - always brake when the situation requires it.)
Anticipation goes hand in hand with acceleration/braking. Look ahead of you - far ahead - in order to anticipate what sort of speed will be required in the next few hundred meters. If there's is a red light, stop sign, or traffic is slowed or stopped then only accelerate enough so that you have enough energy to coast into the stop. Anticipation could also mean potentially lane changing or accelerating even more in order to maintain an optimal speed. Always scan ahead, and determine what the most efficient course of action is.
Use the Correct Type of Fuel
Most vehicles are designed to run on regular gasoline, while some are designed to use premium fuel. Click here for more information on what type of fuel is best for your vehicle.
Coasting (or gliding as some call it) follows naturally from anticipation. Coast whenever possible instead of speeding up to a stop, and then applying the brakes. For the best coasting performance, shift the engine into neutral. If the engine is left in gear, there will be a considerable amount of engine braking that will occur. (NOTE: Be mindful of other drivers around you. Slowly coasting up to a stop will frustrate most drivers that are directly behind you. Be respectful of others on the road.)
Stop and go traffic is the least efficient place to drive. It will burn the most amount of fuel per kilometer compared to any other driving environment. It may be more efficient to take a longer route that is less congested, then taking the shorter, congested route. In the event that stopping your vehicle for more then ten seconds or so is necessary, consider turning your car off completely, or at least shifting into neutral. (NOTE: It is important to recognize situations where you must retain the ability to move your vehicle at a moments notice, such as at the back of a line in order to avoid a rear end collision. Always focus on safety first, and fuel efficiency second when it comes to driving.)
Minimize Weight + Improve Aerodynamics
Reducing the weight and improving aerodynamics is a simple yet effective way to increase fuel efficiency. The removal of common items such as roof racks, spoilers, brush guards, trailer hitch, and running boards can reduce the weight and air drag of your vehicle quite a bit. The vehicle can also be driven with the fuel tank mostly empty, as that reduces the amount of fuel that must be carried around at all times, thus reducing weight.
Another way of ensuring that your vehicle is running at its most efficient state is to ensure that the suspension and steering systems are functioning correctly.
None of the these techniques can drastically increase your fuel efficiency on their own. They are meant to be applied in unison, and when done correctly, fuel economy can improve by as much as 50%.