Possible Clues:

• Hardly economical transport
• Joke about second crossword solver not starting 10 3
• It's frequently filled up
• Large car with a high petrol consumption
• Expensive choice for a commuter
• Politically incorrect vehicle
• Car with poor mileage
• Big wheels, often
• Humvee or motor home, typically
• Colloquial name for a car that consumes large amounts of fuel