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Sunday, June 18, 2006


Even more ways not to improve your gas mileage

This article I found on Bankrate included a very interesting link. I'd often heard that the EPA had tested dozens of devices that were supposed to improve gas mileage, but had never heard much detail about this. Well, as it turns out, the EPA has posted the results of all these tests online. The reports are quite lengthy, but there are a few interesting things that stand out.

Of the items that the EPA found useful at all, only four of them actually improved fuel economy while the cars were in motion without screwing up emissions (a fifth device they tested was designed to let you use the heater with the engine off, which can be useful but doesn't help in normal driving). Here's the list of what did work:
  1. Two devices that cut off the air conditioning at full throttle.
  2. A continuously variable transmission that drove the water pump.
  3. Aerodynamic mods to reduce drag.

None of the devices that worked without increasing emissions interfered with the operation of the engine itself. The methods that did result in unacceptably high emissions were a cylinder deactivator (similar to what several OEMs have made work without emissions problems now) and advancing the spark timing.

One interesting thing about the results was that during the '70s and early '80s, many companies submitted their devices to the EPA for testing voluntarily. In more recent times, the EPA has forced companies to have their gadgets tested, with very few people voluntarily having their gas mileage devices tested. Does that mean that fewer companies nowadays believe their devices actually work, and more are just out to scam the public? I don't know, but some of the things they've tested recently seems to be things that only a madman would expect to work.

Another trend is the number of people who kept trying the same unworkable ideas. The most common include magnets on the fuel line and "vapor injection" systems that resemble water/alchohol injection but inject far too little fluid to have any effect. I have to wonder just how the fuel magnet idea got started - it's not like gasoline is magnetic or even contains metal in significant quantities. There were also a number of fuel-heating devices that didn't work, plus one inventor who decided to take the opposite approach and try cooling the fuel.

Pretty useful if you want to see approaches that others have tried and found to be unworkable. If you want more gas mileage, don't try reinventing the square wheel.


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