The gas guzzler tax doesn't really play a part in purchase decisions because almost no American brand car is subject to the tax. Heavy and powerful cars can get pretty good highway mileage with aerodynamics and a long overdrive gear, but their city mileage will be much lower, e.g. the 500hp Corvette Z06 gets 15mpg city/24 mpg hwy and pays no gas guzzler. The Pontiac G8, a heavier sedan with a 361hp V8, gets the same mileage. BTW minivans are also light trucks and exempt from gas guzzler.

I think CAFE did much more to discourage car sales vs. light trucks because minivans and SUVs counted towards the 21 mpg truck average instead of the 27 mpg car average. They were really boxed in to a certain product mix in order to meet the CAFE average, and small cars became their giveaway loss leaders, see Chevy Cavalier and Aveo.

I think the one part of the tax code regarding vehicles is the tax disadvantaged position that cars and small trucks, vans under 6,000 pounds gross vehicle weight (GVW) have. A truck, van, or SUV over 6.000 pounds can be depreciated over 5 years and take a Section 179 deduction (up to $25K), just like computers and other 5 year property. Depreciation on cars is limited to a maximum of $10,960 the first year, $4,800 the second year, $2,850 the third year and $1,775 each year thereafter. If you have a car that costs $35-40K, it takes forever to depreciate it. If you level the playing field between cars and large trucks, people would buy more fuel efficient cars.