The compilation covers Midnight Oil's entire career, starting with their 1978 self-titled album, and includes tracks from all their studio albums and EPs. Given its comprehensive track list, the two-disc Essential Oils effectively supplants Midnight Oil's previous greatest-hits compilation, 1997's one-disc album 20,000 Watt R.S.L. There is only one track on 20,000 Watt R.S.L. ("What Goes On") that is not included on Essential Oils.
Essential Oils contains eleven songs that were included on Flat Chat (2006), an 18-track compilation of Midnight Oil's heavier rock songs. The Flat Chat tracks that do not appear on Essential Oils are "Section 5 (Bus to Bondi)", "Tell Me the Truth", "Stand in Line", "Pictures", "Written in the Heart", "Mosquito March" and "No Time for Games". Essential Oils contains liner notes by American music journalist David Fricke. The album charted at number 7 on the ARIA Charts and it peaked at number 25 on the Official New Zealand Music Chart.