The problem is, fuel efficient cars weigh less, and therefore do less damage to the road.
That's not always true. There are hybrid SUVs now that weigh more than my all-gas camry, but get the same MPG.
The taxing should be use-based. I'm not saying eliminate gas taxes entirely -- there should also be an incentive to drive a fuel efficient vehicle. But they should be lessened and an alternative taxation method formed like this GPS idea or increased toll roads.