Late model vehicles use a system called “Adaptive Knock Control” which uses sensors to detect spark knock from the engine. These systems are calibrated for normal driving under standard weather conditions. The system is transparent in its operation and is typically limiting efficiency and engine power in hot, dry weather. With premium fuel averaging a price 7% more than regular, the fuel economy benefit almost always covers the added expense. An additional benefit is increased engine power and the higher concentration of detergents in premium gasoline.
This is something everyone knows about, but few people actually do. It cannot be understated how important tire pressures are to fuel economy, especially on 2004 and newer hybrids with their larger tires and wheels. Even if the vehicle has a tire pressure warning system the tires can be low enough to affect mileage without triggering a warning light.
A good product to help with this is a set of pressure sensing valve stem caps. Available at parts outlets in varying pressures, the sensors screw on in place of the valve stem caps. When the pressure in the tires falls, the caps turn progressively from green to red. They can easily be glanced at with a quick walk around the car.
In order to simulate a conventional car during electric only operation, Toyota and Lexus have engineered a “Creep” feature into the hybrid system. This mimics the forward creep of a conventional automatic transmission by slightly engaging the electric drive motor when the brake and accelerator are both released. The feature remains active until sufficient pressure is applied to the brake pedal. Unfortunately the pressure required is more than many drivers are used to.
To re-train yourself, switch either the multi information display or navigation system to the power flow screen (the one with all the moving arrows and pictures of parts). With the vehicle on and in “D”, vary the pressure on the brake pedal while watching the arrow from the battery icon go on and off. If the arrow is on, there is power being sent to the electric motor. The resulting battery discharge will cause the gas engine to run longer and more frequently.
The hybrid and engine control system has only two purposes. It is intended to achieve the highest possible fuel economy with the lowest possible emissions. This system is extremely fast and intelligent, but has one big problem—your right foot. The computers are constantly adjusting the throttle of the gas engine, electric motors and transmission gear ratios. Some of these corrections happen many times per second. However, every time the accelerator pedal changes position, the computers must start all over again. Using the cruise control and making smooth transitions increases the amount of time that the vehicle spends at maximum efficiency.
The wonderful thing about Toyota and Lexus hybrid vehicles is the way each part of the system is set up to do its work under the conditions where it is most efficient. The large electric motors used to drive the vehicle are extremely powerful and efficient at low speeds.
Forget everything they told you in Driver’s Ed. The most efficient way to get up to speed is to accelerate rapidly (not dangerously or recklessly) to cruising speed. This allows the electric motor and battery pack to do the hard work while simultaneously operating the gas engine at high throttle and low speed, where it is very efficient.
The single most powerful fuel economy tool at your disposal is the regenerative braking system. At any speed above 5-10 mph, the electric motors are the primary braking system on the vehicle. Rather than converting the vehicle’s kinetic energy into heat, the hybrid system uses it to recharge its batteries. The electric motors become generators, recovering a large amount of the energy used to accelerate. All Toyota and Lexus hybrids are still equipped with a conventional braking system, but it is largely intended for low speeds and severe braking.
The best technique is to lightly apply the brakes well in advance. Although very little slowing occurs, a large amount of electricity is generated. This is more effective than braking late, which limits how much energy can be recovered. Once again, use the power flow screen to observe the system in action. The “Consumption” screen on many vehicles will also show green “E” icons, indicating the amount of energy recovered for each five minute period.
While the original Prius was the only vehicle to be equipped with a special, hybrid-only tire, it is still important to mount proper replacement tires. In 2004, Toyota and Lexus began mounting standard passenger car tires on hybrid vehicles following complaints about the ride and noise of the special hybrid-only tires. However, Toyota and Lexus engineers still test and approve certain tires for hybrid vehicles based on the rolling resistance of the particular tire. This has a large effect on fuel mileage. Certainly, quieter and longer lasting tires are available, but fuel mileage is often compromised.
Wheel alignment is another factor in fuel economy, as well as tire wear. Many hybrid vehicles, especially the early Prius, had alignment angles specified to minimize drag and maximize efficiency. The result is sensitivity to crosswinds on the highway and steering that does not track well at higher speeds. This can be remedied easily by altering the alignment slightly, but again there would be a loss of fuel mileage.
While the weight of passengers and cargo matters little on the highway, it has a large effect in stop and go driving. Try to limit any heavy cargo when possible. It is also recommended that hitch or rear mounted racks be used if cargo has to be carried on the outside of the vehicle. Roof racks and rooftop cargo carriers are horribly inefficient. Try tying a parachute to the back of your bicycle for a demonstration.
This one isn’t very popular, but it’s a big one. Despite everything that has been done to reduce friction and make cars more aerodynamic, the physics have not changed. It still takes an enormous amount of power to overcome drag at highway speeds. It varies by the vehicle, but large gains in fuel economy can be had by reducing speed even a few mph. Thanks to the fuel economy information displayed it is possible to see this effect in real time.
For an eye-opener, drive on the interstate and set the cruise control at various speeds while watching the instant fuel economy reading. Slow down to 55 mph if you dare and find out that you really can get the mileage printed on your window sticker…..then get run over by a semi truck.
Nobody will blame you for not doing this one. It is Tucson, after all. The problem is that a large amount of power is required to run the air conditioning system, and that power uses fuel. This is less of a concern on newer generations of hybrids, which use an electric A/C compressor. If you drive an early Prius, the engine has to run for the air conditioner to operate. There is an “ECON” button which allows the engine to shut off at a stop. I’m not sure why they used “ECON”. It should say “BAKE”, because that’s what happens to the driver after 30 seconds in the summer heat. Raising the temperature will cause the compressor to use less power. Turning it off is even better. In the end, though, there are better ways to save fuel.