Which component compatibility may be affected by ethanol blends in fuel?

• A. Seals and materials compatibility may be affected.
• B. Battery capacity is increased.
• C. Spark plug heat range is unaffected.
• D. Oxygen sensor becomes unnecessary.

Answer: (A)

Ethanol blends can affect component compatibility because ethanol acts as a solvent in the fuel system, interacting with seals, gaskets, hoses, and other elastomeric and plastic materials. Many elastomers aren’t fully resistant to ethanol, so exposure can cause swelling, shrinking, softening, or hardening of seals and O-rings. This can lead to leaks or degraded performance over time. Ethanol's tendency to attract moisture can also promote corrosion or degradation of coatings and certain metals if the materials aren’t designed for ethanol-rich fuels. To prevent issues, fuel-system components are specified to use ethanol-compatible materials or seals.

Battery capacity is a property of the electrical system and isn’t determined by fuel composition. Spark plug heat range relates to combustion temperature and operating conditions, not the core issue of material compatibility with ethanol blends. An oxygen sensor is still needed to monitor the air-fuel ratio; ethanol blends do not remove the requirement for this sensor.