Final answer:
In testing gasoline additives, the consumer advocate may assess the octane rating, which signifies fuel quality and ability to prevent engine knocking. Higher octane ratings, achieved by additives like ethanol, lead to better fuel performance and safety but require careful choice to avoid environmental harm.
Step-by-step explanation:
When a consumer advocate conducts a test of two popular gasoline additives, they may assess various aspects such as combustion efficiency, octane rating, fuel economy, and emission levels. The octane rating is particularly crucial as it indicates the fuel's ability to burn in a combustion engine without knocking or pinging, which are signs of premature combustion. Higher octane-rated fuels and additives, like ethanol, prevent this premature combustion, thereby improving performance and safety.
Tetraethyllead used to be an effective antiknock agent, but due to toxicity concerns, it was replaced by other compounds like MTBE, which later faced bans due to groundwater contamination. Consequently, more environmentally friendly alternatives like ethanol, derived from renewable resources such as corn and sugar cane, are increasingly used.