2-Ethylhexanol

2-Ethylhexanol (2-EH; CAS 104-76-7) is a branched C8 primary alcohol produced commercially as a co-product of oxo synthesis (hydroformylation). It is a colorless, slightly oily liquid with a mild, sweet odor and limited water solubility. At the fuel-additive concentrations where it appears (10–15% in diesel treatments), it functions as both a coupling agent — helping dissolve 2-EHN and other actives in the petroleum distillate carrier — and a mild lubricity contributor via its hydroxyl group's boundary-lubrication properties.

In the CarCareTruth context, 2-ethylhexanol appears in diesel fuel additive formulations containing 2-ethylhexyl nitrate (2-EHN). The alcohol is a thermal decomposition product of 2-EHN, and some formulations include it deliberately as a co-solvent. At the mixture concentrations found in consumer diesel treatments, 2-ethylhexanol's primary hazard pathway is brief inhalation during the tank-pour scenario; the compound is more volatile than the heavy-aromatic naphtha carrier and contributes to the inhalation exposure window alongside 2-EHN vapors.

The compound is biodegradable and is not classified as a persistent, bioaccumulative, or toxic (PBT) substance under EU REACH. Its aquatic toxicity at finished-product concentrations is low.