Grapefruit, But I adore Grapefruit essential oil, and use it regularly in the diffuser. When I first began Learning about aromatherafy in the '90's, I expected grapefruit essential to smell rather harsh and bitter. I was glad to be so wrong when I enjoyed my first whiff. Instead, Grapefruit oil has a pleasantly sweet. Tangy/tart aroma that blends well with a number of other essential oils.For a lovely aromatic combination, try blending it with frankincense oil. I also love it blending with conifers like fir needle oil.