And I'd be opposed to that. The federal government is so bloated, they probably have enough vehicles for the next ten years if they were to stop doing all the things not authorized by the Constitution.
Efficiency is not the only consideration when buying a vehicle. I, personally, don't want a vehicle that sacrifices safety for efficiency.
The government shouldn't be using pork or other inducements to bias the market towards one consideration. Consumers knows their own needs.
If government wants to promote efficient, it should start by being less wasteful itself. Right now its the worst example in human history.