why is mtbe used as a gasoline additive
Methyl tert-butyl ether In the US it has been used in gasoline at low levels since 1979, replacing tetraethyl lead as an antiknock (octane rating) additive to prevent engine knocking. Oxygenates also help gasoline burn more completely, reducing tailpipe emissions and dilute or displace gasoline components such as aromatics (e.g., benzene). Before the introduction of other oxygenates and octane enhancers, refiners chose MTBE for its blending characteristics and low cost.
Castoreum In the United States, the Food and Drug Administration lists castoreum extract as a generally recognized as safe (GRAS) food additive.[12] In 1965, the Flavor and Extract Manufacturers Association's GRAS program (FEMA 2261 and 2262) added castoreum extract and castoreum liquid.[13] Product ingredient lists often refer to it simply as a "natural flavoring." While it is mainly used in foods and beverages as part of a substitute vanilla flavor,[14] it is less commonly used as a part of a raspberry or strawberry flavoring.[15] The annual industry consumption is very low, around 300 pounds,[16] whereas vanillin is over 2.6 million pounds annually.[17]