Related Clues:

• Rembrandt's medium
• Some change it regularly
• Helium, for one
• Tanker cargo
• Hydrocarbon fuel
• What to 'fill 'er up' with
• The 'it' in 'Step on it!'
• Antacid target
• Bunch of fun
• Alternative to oil
• Civic need?
• Exxon product
• Really good time
• You may step on it in a rush
• Fossil fuel