Improving fuel economy with higher octane and stop-start

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Close-up of the front panel of a gasoline station pump. The octane numbers go from 87 all the way up to Ultra 93.

Try some 89 octane next time. The added fuel economy is worth your while. (Photo Credit: CC BY-ND/Matthew Oliphant/Flickr)

As the search for better fuel economy motors on, it is curious that two very simple methods for boosting mpg are typically ignored. As mileage boosters, using high octane gas and stop-start technology could squeeze more from that tiger in your tank.

Two fuel economy tricks, with obstacles

While using high octane fuel and employing stop-start methods may seem easy, there are actually some obstacles that prevent U.S. consumers from fully utilizing them, according to Automotive News. Yet ultimately, the problems can be overcome.

Take high octane fuel

Using high octane fuel works to improve engine combustion via a higher compression ratio. The compression ratio is how much the engine squeezes the air it intakes when forming the air/fuel mixture before ignition and the expansion that leads to the production of mechanical energy. If you use a high octane fuel – a fuel that offers a higher minimum octane rating – your vehicle’s powertrain can achieve a greater compression ration, which amounts to increased fuel efficiency.

The use of a turbocharger is also more effective with high octane levels of gasoline, according to Stephen Ross, the combustion technical leader at Ford Motor Co. Such things can help the U.S. auto industry achieve its goal of a corporate average fuel economy of 54.5 mpg by 2025, but automakers and oil companies must be on the same page when it comes to octane level consistency. Ninety-one octane should mean just that, not an approximate that is actually somewhat lower.

Stop-start: A hybrid bonus

Current generation hybrid cars achieve greater fuel efficiency via stop-start technology, or simply stop-start. When the vehicle isn’t in motion, the engine automatically shuts off, eliminating idling that wastes fuel/power and causes wear and tear on the engine.

According to Mike Omotoso of J.D. Power and Associates, stop-start boosts fuel economy by as much as 10 percent. Brett Smith of the Center for Automotive Research in Ann Arbor, Mich., notes that once the federal government starts giving tax credits to owners of stop-start system-enabled hybrids and EVs by 2017, fuel economy should improve across the board.

Stop-start has become increasingly common in hybrid and fully electric vehicles, but some have advocated using the stop-start technique on older, internal combustion engine cars. While it is possible to shut off the engine manually each time the vehicle comes to a stop – saving on fuel costs – using the stop-start technique places undue stress on a car’s starter system. Damage to the battery, alternator, gears and starter motor can occur, and each is expensive to replace, thus negating the fuel savings.

A champion of mid-grade gasoline


Automotive News

Start-stop system Wiki

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