Modifiers matching fuel:

• reactive,
• synthetic,
• heavier,
• solid,
• liquid,
• lighter,
• common,
• combustible,
• dead,
• volatile,
• organic,
• manufactured,
• dense,
• rich,
• thinner,
• up,
• supporting,
• conventional,
• traditional,
• foreign,
• propellant,
• small,
• new,
• down,
• alternative,
• familiar,
• hazardous,
• vehicular,
• light,
• miscellaneous,
• local,
• separate,
• basic,
• vaporizable,
• gaseous,
• fluid,
• industrial,
• individual,
• normal,
• fibrous,
• main,
• special,
• commercial,
• heavy,
• typical,
• nonrenewable,
• practical,
• granular,
• destructive,
• corrosive,
• abrasive,
• taxable,
• nonwoody,
• thermal,
• artificial,
• inhomogeneous,
• fine,
• off,
• modern,
• diverse,
• domestic,
• beneficial,
• real,
• simple,
• suitable,
• compressible,
• difficult,
• environmental,
• toxic,
• cheap,
• several,
• intermediate,
• motor,
• nuclear,
• appropriate,
• renewable,
• advanced,
• dangerous,
• single,
• consumable,
• clean,
• automotive,
• auxiliary,
• future,
• porous,
• dry,
• extra,
• actual,
• friendly,
• medical,
• ordinary,
• dirty,
• innovative,
• valuable,
• needed,
• raw,
• biological,
• unhealthy,
• key,
• ignitable,
• uniform,
• loose,
• inexpensive,
• particular,
• smaller,
• indigenous,
• dirtier,
• supplementary,
• precious,
• complex,
• indoor,
• nonpolar,
• residual,
• technical,
• vegetative,
• expensive,
• essential,
• mundane,
• pure,
• direct,
• commonplace,
• odd,
• major,
• available,
• standard,
• safe,
• explosive,
• useful,
• cryogenic,
• harmful,
• herbaceous,
• oxidizable,
• metabolic,
• flammable,
• supplemental,
• finished,
• discrete,
• chemical,
• macromolecular,
• physiological,
• old,
• wet,
• usable,
• unconventional,
• convenient,
• hard,
• compressed,
• regular,
• particulate,
• specialized,
• residential,
• efficient,
• soluble,
• sensitive,
• refined,
• abundant,
• starting,
• possible,
• secondary,
• homogeneous,
• cleaner,
• competitive,
• benign,
• sustainable,
• strategic,
• damaging,
• natural,
• exotic,
• desirable,
• primary,
• unprocessed,
• important,
• carbonaceous,
• base,
• inflammable,
• unwanted,
• costly,
• powdered,

Simple categories matching efficient:

• appliance,
• network,
• port,
• equipment,
• stove,
• vehicle,
• business,
• facility,
• process,
• activity,
• technology,
• device,
• institution,
• product,
• ministry,
• commodity,
• gear,
• energy,
• creature,
• ionization,
• utility,
• fuel,
• component,
• meat,
• ballast,
• way,
• service,
• system,
• practice,
• measure,
• engine,
• laser,
• truck,
• action,
• fixture,
• transport,
• organization,
• machine,
• automobile,
• thing,
• unit,
• performance,
• means,
• manner,
• radiator,
• container,
• item,