my BMW 3 Series G20/G21 (2019-2024) fuel economy has dropped significantly, what could be wrong?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface with the engine off.
• Disconnect the battery for safety.

2. Replace Air Filter

• Sub-steps:
  1. Locate the air filter housing.
  2. Open the housing by unclipping or unscrewing it.
  3. Remove the old air filter and inspect the housing for debris.
  4. Install the new air filter, ensuring a snug fit.
  5. Reassemble the housing and secure it.

3. Check and Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil covers if necessary.
  2. Disconnect the ignition coils and pull them out.
  3. Use a spark plug socket to unscrew and remove the old spark plugs.
  4. Check the gap on the new spark plugs and adjust if needed.
  5. Install the new spark plugs and reconnect the ignition coils.

4. Inspect and Repair Exhaust System

• Sub-steps:
  1. Visually inspect the exhaust system from the manifold to the tailpipe for any signs of leaks or damage.
  2. If leaks are found, mark the locations for repair or replacement.
  3. Use exhaust sealant or replace damaged components as necessary to ensure a sealed exhaust system.

5. Check Tire Pressure and Condition

• Sub-steps:
  1. Use a tire pressure gauge to check each tire's pressure.
  2. Inflate tires to the manufacturer’s recommended PSI.
  3. Inspect tires for uneven wear or damage, replacing them if necessary.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Tire pressure gauge
• Screwdrivers
• Replacement air filter
• Replacement spark plugs

Parts Required:

• Air filter
• Spark plugs
• Exhaust sealant (if applicable)
• Replacement tires (if needed)

Estimated Repair Time: 2-4 hours

Safety Warnings:

• Disconnect the battery before working on electrical systems.
• Allow the engine to cool before inspecting any components.