ASE Auto Maintenance and Light Repair Certification (G1) Practice Test 2025 - Free Auto Maintenance Practice Questions and Study Guide

Worn spark plugs can lead to reduced fuel efficiency because they may not create a strong enough spark to ignite the air-fuel mixture in the combustion chamber effectively. As the spark plugs wear, they can become fouled or have an improper gap, which causes misfires or incomplete combustion. This inefficiency means that the engine must work harder to generate the same amount of power, leading to increased fuel consumption. Therefore, the result of having worn spark plugs is a decrease in the vehicle's overall fuel efficiency, which is critical for both performance and economic operation.

In regard to other choices, worn spark plugs could potentially impact engine temperature positively or negatively, but that is not a guaranteed result exclusively linked to their condition. Additionally, worn spark plugs do not correlate with shorter ignition times; they typically lead to longer ignition times due to misfires. Enhanced engine performance is the opposite of what occurs with worn spark plugs, as they degrade the engine's efficiency and output.