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petdave -> RE: Americans should stop whining about gas prices (7/16/2008 8:37:19 PM)
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quote:
ORIGINAL: fluffypet61
Does anyone remember the national 55mph speed limit? We got better gas mileage then.
Did we? There's so much discussion on this right now on the web that i can't find squat for facts. However, as a "car guy" let me put out the following:
The 55 mph limit didn't take place in a vacuum. 1974 saw the early phases of emissions controls, robbing engines of both power and mileage. The vast majority of autos drew fuel through carburetors. The average American car was quite large.
By 1984, every domestic manufacturer had reduced the size of their cars dramatically. Cars like the early Honda Civic and Volkswagen Rabbit barely weighed a ton, lighter than just about any four-wheeled vehicle on the market today. Fuel injection was now more or less the standard, and the various bugs with FI, emissions controls, and electronic ignition had largely been worked out. Aside from Chrysler's aging Torqueflite, most cars were using 4-speed automatics or 5-speed manuals to make better use of the engine's peak torque, backed by taller gear ratios to reduce engine rotation at a given speed.
Fast-forward to today. Average fuel economy has dropped, i would suspect, largely due to the SUV fad. Heavy vehicle + large engine = poor fuel economy. Cars on average are heavier due to more electronics and standard features as well as safety devices. However, manufacturers are paying much more attention to aerodynamics than they did twenty years ago. We've moved up to six and seven-speed transmissions with electronic controls. Advances in computer modeling and metallurgy have given us engines that are more efficient and cleaner-burning (and even lighter, as a bonus) than their predecessors.
As a result, for many automobiles, a given reduction in speed does not automatically equate to a reduction in fuel efficiency. At highway speeds on a flat road, the largest factor in engine load is aerodynamic drag. A 2007 Corvette gets roughly the same mileage on the highway that my Mazda3 gets around town, despite having an engine nearly three times as large. With both cars doing a steady 100 MPH, i would bet money that the 'Vette would be burning less fuel.
And, if anyone has read this far, one item that people are ignoring with regards to the "60 MPG Euro car" is that a much higher percentage of cars sold in Europe are Diesel. The EPA has virtually killed Diesel sales in the U.S. with stringent emissions, and their strict requirements for fuel formulation have brought it to the point of being almost a dollar higher than regular unleaded (at least in this area), whereas ten years ago i could often find Diesel for LESS than regular unleaded in the summer (in the winter, demand for home heating oil would drive up the price, since they're very similar in formulation)
Thank you.
/cargeek
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