Possible Clues:

• Well brought up, but lacking refinement?
• Source of fuel turns cloudier
• Tanker's tankful
• Sort of cloudier fuel that's unrefined
• Cold ill-mannered type from Greece said it needs refinement
• Cold, ill-mannered type from Greece said it needs refinement
• Well target
• Well disposed to taking it out of The Underground provided it gets refinement
• Unrefined fuel
• Snake swallows unrefined fuel