Category Nuances for heavy_oil:

• working,
• binding,
• difficult,
• supplemental,
• raw,
• traditional,
• industrial,
• liquid,
• inorganic,
• primary,
• viscous,
• alternative,
• organic,
• special,
• fluid,
• inexpensive,
• ignitable,
• dirty,
• costly,
• residual,
• gross,
• base,
• heavy,
• complex,
• carbonaceous,
• rich,
• extraneous,
• original,
• heavier,
• secondary,
• expensive,
• gaseous,
• auxiliary,

Simple Categories for heavy_oil:

• material,
• substance,
• hydrocarbon,
• fuel,
• mixture,
• agent,
• deposit,
• oil,
• fraction,
• contamination,
• fluid,