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130+mph when the average urban speed limit is under 55 is asinine. I have always said that they ( manufacturers ) can gear them to get sufficient torque with less top end speed and get better mileage.

You're running into too many practical concerns. My 1.6L, 115 horsepower Nissan Sentra can exceed the speed limit on any highway in the United States. Tell me, how much weaker do you want to make them?

You can't gear them to reduce top speed without reducing fuel economy. If you take any given engine, and gear it so that the final gear won't send the car above the speed limit at maximum RPM, you'd be in a situation where, to run at highway speed limit, you'd be running the engine at near max RPM. This is extremely bad for fuel economy, not to mention it increases wear on the components.

You could re tune the engines to generate maximum torque at low RPM and put an RPM limiter on it. However, even with the most extreme biasing towards torque at low RPMs, I think you'd still be turning too many rpms in the final gear to move at highway speeds.

There is a chance you might be able to do this with diesel engines, which naturally generate a lot of low end torque but don't have high redlines.

The only way to realistically do this is to either electronically limit the maximum speed of the car or produce cars with exceptionally weak engines.

The problem is that what you're talking about is somewhat mutually exclusive. A very tight gear ratio increases fuel economy, but that tight gear is what also allows the vehicle to reach very high speeds given enough time to accelerate and depending on torque generated by the engine.

You can't gear them to reduce top speed without reducing fuel economy. If you take any given engine, and gear it so that the final gear won't send the car above the speed limit at maximum RPM, you'd be in a situation where, to run at highway speed limit, you'd be running the engine at near max RPM. This is extremely bad for fuel economy, not to mention it increases wear on the components.

DING DING DING - you win the cookie :-)

I just added a K&N Cold Air Intake to my O7 Mustang. The first thing the hand-wringers and envirowhiners will see is that I added 18-24 HP to my already "TOO POWERFUL" engine. But they will cover thier ears when I mention that my hwy mileage went from 24.8 MPG to 28.6 MPG.

They can't seem to understand that with a mid to high performance engine - more power = BETTER GAS MILEAGE

Although I have to admit the much improved throttle response, accelleration suction sound and the new deeper growl have thier attraction too ;-)