Your proposal to raise gas taxes by 25 cents to cut consumption is way, way off the mark. For most U.S. drivers a 25-cent increase in the cost of gasoline would be a nuisance tax, not a disincentive.
The following table of gas taxes in the Western world in 1987 illustrates the point: United States, 29 cents; Australia, 65 cents; West Germany, $1.34; United Kingdom, $1.53; France, $2.32; Japan, $1.47; Denmark, $2.93; Italy, $2.78.
It would appear, then, that an increase of $1 or $2 in the gas tax would be needed to create a disincentive to gasoline consumption.
The reason of course, is that a 25-cent increase is marginal to other costs of operating a car: insurance, taxes, maintenance, parking and the number of commute miles to and from work.