$4000 per vehicle for a new computer programming chip ?
anyway, talk about pushing things to the absurd to lose your point.
Well yeah, I am assuming you are talking about a government program, and $4000 is probably a conservative amount, given the government pays this much for toilet seats and hammers in most government contracts. As I pointed out, and you seem to be ignoring, not every car is compatible with chip technology. In fact, those which are compatible, would require a different chip for every make, model, and engine configuration. That still leaves an estimated 50% of all vehicles not covered, because they were built before we put chips and computers in cars. Those vehicles would require new engines, which would cost tens of thousands of dollars, because we can't expect Joe Poor to pay for your stupid mandate. AND, even IF this was done, there is no way to possibly enforce compliance, you would have a major problem with black market cars, or shade-tree solutions and workarounds. People really don't like being told they can't have something they know is available.
This is the main point of contention, and why you continually run into trouble with your ideals. You, like many socialists, fail to factor in the human element. You assume, because something looks good on paper or some study indicates something, that is just how things should be, but they never factor in the human equation. Human behavior changes the results of the study or blueprint, and it often doesn't work out as planned. This is the case with your idea here, you have read some statistic that says cars save X% on fuel if they operate at 55 instead of 70, but in practice, the human element comes into play, people don't drive 55, and the savings is never realized.