We Be Sippin': Nine Technologies that Significantly Reduce Fuel Consumption

June 29, 2012 at 12:14 pm by

We Be Sippin’: Nine Technologies that Significantly Reduce Fuel Consumption

From the July 2012 issue of CAR and DRIVER magazine

Squeezing every last mile out of a gallon of fuel is paramount in today’s heavily regulated era of motoring, so carmakers and suppliers are looking everywhere for efficiency improvements. And it’s not just through electrification and hybridization—lots of the gains are incremental and relevant to internal-combustion engines. Here is a list of nine technologies that, taken together, add up to a significant reduction in fuel consumption for cars whose engines still suck, squeeze, bang, and blow.


Drag destroys fuel economy, especially at highway speeds. Manufacturers massage the aerodynamic efficiencies of everything: headlights, side mirrors, rear bumpers, windshield wipers, you name it. Some advances—drag-reducing flat underbodies, for example—are hidden. Others, such as protuberances on headlights to direct air around side mirrors, are visible. The Chevy Cruze Eco, among ­others, features automatic shutters that control airflow to the radiator, a huge source of drag. They automatically close during low-load situations (cruising at 75 mph). Partially blocking the radiator also helps warm the engine faster, improving efficiency and lowering emissions.


Just 10 years ago, six-speed automatics were found only in luxury and high-performance cars. Today, six-speeds are the norm while seven- and eight-speed autos dominate luxo rides. Soon, ZF will launch its 9HP nine-speed automatic, which it claims will deliver 10-percent-better fuel economy. The overall ratio spread (first-gear ratio divided by top-gear ratio) is more important to fuel economy than simply adding more speeds, though—with modern electronic controls, automatics rifle through the gears, keeping revs to a minimum. Another fuel-saving option is ultra-tall gearing (final drive or top gear) fitted to engines with sufficient low-end torque to spin at near-idle speeds when the car is going 70-plus mph. Thanks to gearing, sports cars such as the Corvette avoid a gas-guzzler tax.

Electric/Clutched Auxiliaries

BMW led the way with clutched alternators that only recharge the battery when coasting—or when absolutely needed. This reduces the load on the engine and thus saves at the pump. Electric-assist power steering is rapidly becoming the norm because, again, the electric motors don’t constantly draw power from the engine, as does the pump of a traditional hydraulic power-steering setup. The specific savings is tough to nail down because it differs in every car and with every driver, though ZF says its Servolectric range of steering racks can save about a tank of gas every year.

Reduced Weight

How can automakers satisfy the conflicting demands of government entities such as NHTSA, which wants cars to withstand head-on collisions with dump trucks, and the EPA, which wants 1 billion mpg? The answer is simple, if very, very complex: Manufacturers have to make their cars lighter and stronger. Carbon fiber fills the bill—it’s both light and strong but also extremely expensive. Lightweight metals (aluminum and magnesium) are currently supplementing steel structures, and we will see more of those metals before carbon-fiber construction becomes commonplace. But one thing is certain: The less weight an engine needs to move, the less fuel said engine will consume.


The fundamental advantage here is that a gallon of diesel fuel contains more energy than a gallon of gasoline. Compression-ignition engines run at lower revs and generate gobs of torque, making them incredibly practical for daily driving. According to EPA combined estimates, Volkswagen’s 2.0-liter turbo-diesel in the Golf burns one gallon of diesel every 34 miles. Compared with the 27-mpg GTI (a turbocharged 2.0-liter gas engine), the diesel is 26 percent more efficient. Diesels generally cost more because they require more-expensive emissions controls, but expect to see more of them in the future.

Stop-Start Systems

The few carmakers that currently offer stop-start (a system that a­utomatically shuts down the engine when a vehicle is static) do not get a huge bump in EPA fuel-economy ratings. According to Mazda, stop-start is good for only 0.1 percent on the EPA city-driving loop because cars are not idle for more than a handful of seconds during that test. In the real world, where commuters can end up sitting in stop-and-go traffic for long periods of time, legitimate savings exist. However, the added peace and quiet these systems provide at standstill is offset by an annoying start-up lag when it’s time to move again.

Cylinder Deactivation

Cutting fuel, spark, and valve operation to half of the available cylinders has historically been a technique reserved for engines with eight or more cylinders. Volkswagen recently introduced a turbocharged 1.4-liter inline-four with cylinder deactivation and claims the engine can save a gallon of gas every 336 miles at a constant 45 mph. The use of advanced supporting technologies, such as electronically controlled engine mounts and noise cancellation, is likely to expand the application of this fuel-saving strategy.

Low-Rolling-Resistance Tires

The secret to the newest low-rolling-resistance tires, such as the Ecopia EP422 from Bridgestone, is how engineers have been able to reduce hysteresis, or the natural deflection, deformation, and elastic delay that occur when a rubber circle that carries thousands of pounds rolls. By reducing hysteresis, the tires waste less energy in the form of heat. Bridgestone says that during the 65,000-mile estimated life of the tires, the EP422 can save more than 100 gallons of gas when compared with the company’s standard Turanza EL400. Lessons learned developing low-rolling-resistance rubber eventually will factor into all tire designs.

Smaller, Turbo Engines

Marketers of turbocharged engines often use tag lines like “V-8 power with V-6 efficiency.” This is not exactly true: 400 horsepower, for example, is 400 horsepower whether it comes from four, six, or eight cylinders. An engine with a smaller displacement has less reciprocating mass, lower friction, and ample gas-saving potential in low-load situations. The greater gain comes when all that “V-8” power isn’t called upon and a forced-induction engine is basically operating in a naturally aspirated mode. For drivers, staying out of the boost—where the power lives—is the key to saving gas.

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