How was ethylene dibromide used in leaded gasoline?

In leaded gasoline, ethylene dibromide (also known as ethylene bromide) served as a chemical scavenger.12

While tetraethyl lead was added to gasoline to prevent "engine knock," its combustion produced lead oxide, which would otherwise accumulate as harmful deposits within the engine cylinders. To address this, small quantities of ethylene dibromide—often mixed with ethylene dichloride—were added to the fuel. During combustion, the bromine reacted with the lead to form a compound that was expelled from the engine through the exhaust, thereby preventing the buildup of lead deposits.12