The molecular formula C8H18 may refer to:
Octane (n-octane)
2-Methylheptane
3-Methylheptane
4-Methylheptane
3-Ethylhexane
2,2-Dimethylhexane
2,3-Dimethylhexane
2,4-Dimethylhexane
2,5-Dimethylhexane
3,3-Dimethylhexane
3,4-Dimethylhexane
3-Ethyl-2-methylpentane
3-Ethyl-3-methylpentane
2,2,3-Trimethylpentane
2,2,4-Trimethylpentane (isooctane)
2,3,3-Trimethylpentane
2,3,4-Trimethylpentane
2,2,3,3-Tetramethylbutane
