NEW YORK (CNNMoney) -- Ordinarily, you want a GPS navigation system to show you the quickest way to get where you're going. But with gas prices over $4 a gallon in some cities you might rather know the way that uses the least gasoline.
Some new navigation systems can now do that.
But if you're in a rush you should know this: Sometimes using less gas might take a little longer.
While ordinary GPS routing relies on data like the expected average speed on various roads, "Green Routing" or "Eco-Routing" adds in other factors, said Mark Burfeind, a spokesman for TeleNav, a digital mapping company that supplies an "Eco-Route" system used in some Ford Motor Co. vehicles.
Among the factors Ford's "Eco-Route" system looks at:
Of course, many GPS systems already take traffic into account, but it's given greater importance when calculating an "Eco-Route." There may be cases in which driving through a traffic jam would be quicker because it's more direct, but driving around it would actually use less fuel.
Also, slower roads can be more fuel efficient. Once a car is going fast enough to use its highest gear, every mile per hour faster reduces fuel economy. So driving on a 50 mile per hour road, provided its straight and without stop lights, might be be preferable to a 65 mph rural freeway.
Compared to using the "fastest" route, Ford says its researchers found that using the "Eco-Route" option offered as much as 15% reduced fuel use in some of their vehicles. Map data company NavTeq, creator of a similar system that will be used by Hyundai in Europe, estimates a more modest 6% improvement.
December is chockablock with big financial news that is bound to move the markets. They range from momentous rate decisions at central banks to IMF's decision on China's currency. More
Yahoo stock has been a big loser this year. Some analysts and investors are wondering if time has come for Yahoo to get rid of Marissa Mayer and find a new CEO. More
Shoppers around the country braved the crowds to get their hands on the best Black Friday deals. More