Starting fluid

Starting fluid is a mixture of diethyl ether, volatile hydrocarbons (heptane, butane and propane), dimethyl ether (as a propellant), and carbon dioxide. It is often useful when starting direct injected diesel engines or lean burn spark engines running on alcohol fuel. Starting fluid works due to the low autoignition temperature of diethyl ether: 360 °F (182 °C).

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Starting fluid comes in a regular or premium grade. The regular grade contains 21-35% diethyl ether. Premium grade starting fluids have a 40-60% diethyl ether content. The rest of the volume is commonly taken by heptane.

Using starting fluid to get the engine running faster avoids wear, especially on rarely used engines. Mechanics, especially amateur mechanics that lack diagnostic machines, sometimes use it to diagnose starting problems. If sprayed into the air intake on a car, it can be used to determine whether the spark and ignition system of the car is functioning, since the engine will run until the starting fluid vapors in the intake system are exhausted. It is used more often with carbureted engines than with fuel injection systems. It is especially useful for starting diesel engines in colder weather as they do not run efficiently until the engine block warms up to a certain degree.

Starter fluid is sometimes used as an inhalant. The majority of the effects are caused by diethyl ether in liquid form rather than as vapor.