They include lower rolling restistantance tires, cylinder deactivation (must have at least 6 cylinders), a start-stop system that kills the engine during idle times, electric power steering so that idt does not load the engine via a hydraulic pump, 6 speed automatic gearbox which can be found in some affordable cars such as the 2009 Chevy Malibu, smaller engine with a supercharger and direct gasoline injection inot the cylinders, in the same way that diesel engines work for nearly 100 years now.
Here is a table that summarizes all these and provides a listing on the basis of bang for the buck.
| U.S. $ Cost/Car | MPG Reduction (%) | Bang / Buck | ||
| 1 | Low rolling resistance tires | 6 | 1 | 167 |
| 2 | Cylinder deactivation | 225 | 4.5 | 20 |
| 3 | 6 speed auto transmission | 260 | 5 | 19 |
| 4 | Electric power assist steering | 180 | 1.5 | 8 |
| 5 | Smaller engine with turbocharger | 750 | 5 | 7 |
| 6 | Start-stop system (kill engine at idle) | 1900 | 5 | 3 |
| 7 | Direct gasoline injection (like diesel engines) | 400 | 1 | 3 |
| 3721 | 18 |
Some interesting observations are as follows: All these technologies are affordable and even if all are combined together the total cost addition to a $25,000 vehicle is relatively small. For example, applying all solutions from 1 to 7 except for 5 yield a total estimate of about $3,000 and an MPG gain of 18%.
However, some of them are not necessarily compatible with each other. For example, changing from a 3 liter V6 to a 2 liter turbocharged engine no longer enables cylinder deactivation.
So if we take a 2009 Ford Fusion that delivers 23 mpg overall, an 18% improvement in fuel efficiency yields 28 mpg. If its user clocks 12,000 per year, he or she will realize a savings of roughly 470 galons of gasoline or $1,400 for a price per gallon of $3.00
The lesson here appears to be that a paradigm shift is necessary to make light duty vehicles both affordable and energy efficient. This paradigm shift includes two major components:
(1) massive reduction in vehicle mass (what we popularly call weight) which will likely bring a reduction in size as well and as an added benefit, there will be normal use for parking stalls labelled "compact."
(2) replacement of high displacement gasoline motors with diesel motors, electric drives or both.
A combination of (1) and (2) can result in susbtantial energy economy at an affodable price. Toyota Prius and Honda Insight are the current and largely convincing proof of this, but the future is bright and promissing.
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