Autos Insider | White House: No more full-size vehicles unless essential

the rules allow agencies to exempt "vehicles used for law enforcement, protective, emergency response or military tactical operations."

That means cabinet secretaries and other government officials who are ferried around in full-size SUVs won't have to shift into smaller vehicles like other government workers.

The policy also allows agencies to buy vehicles that run on E85 ethanol — a fuel mixture that is 85 percent ethanol — to count as advanced-technology vehicles even if they never use the biofuel.

But Obama's three-page order says "alternative fueled vehicles must, as soon as practicable, be located in proximity to fueling stations with available alternative fuels, and be operated on the alternative fuel."