Automakers Tweak Current Models to Improve Mileage

Have you noticed lately how all the car commercials advertise how many miles per gallon the vehicle gets? Such and such vehicle, although it is a huge SUV, gets the best miles per gallon in its class. 

So with the advertising focused on miles per gallon, automakers are tweaking their current models to beat their competition to have the best mileage.
For example, the 2009 Chevy Cobalt has been tweaked to get one more highway mile per gallon than the 2008 Cobalt. The 2009 model will get an estimated 37 mpg, reports the AP and
"Fuel economy is very important," said Greg Peterson, GM’s vehicle performance manager for compact cars, including the Cobalt.  "That is one of the drivers in the changes that we made."
The 2009 Chevy Cobalt will get one more mile per gallon.
How did they get one more mile per gallon out of the Cobalt and its sister car, the Pontiac G5? Engineers varied the intake and exhaust valve timing to make the 2.2-liter four-cylinder engine burn fuel more efficiently.  They arranged with Goodyear Tire & Rubber Co. for tires with lower rolling resistance, and they changed the gear ratios of the five-speed manual transmission so the engine revs more slowly at highway speeds.
Ford engineers added a six-speed automatic transmission, electric power steering and variable valve timing to the Escape and Mercury Mariner small sport utility vehicles to get another two miles per gallon on the highway.
Chrysler engineers took similar measures on several models but also recalibrated gas pedals, changed to more efficient air conditioning compressors and tweaked transmission shift intervals to make them more efficient. The Sebring and Avenger will now get 31 mpg instead of 30.
When a new model is released, the changes should be drastic.  GM says the Cruze, the Cobalt’s replacement coming in the second half of 2010, will get around 45 mpg on the highway.
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