Fire Oil

Fire Oil is created by Alchemists and is used to created other fire-based items.

Source
Fire Oil can be crafted using Alchemy (130); this recipe is taught by Alchemy trainers.

See for catching tips.

Alchemy

 * Elixir of Firepower
 * Fire Protection Potion
 * Elixir of Greater Firepower
 * Elixir of Minor Accuracy

Enchanting

 * Enchant Cloak - Lesser Fire Resistance

Tailoring

 * Crimson Silk Cloak
 * Crimson Silk Shoulders
 * Crimson Silk Gloves