What is an inspection for worsening gas mileage?

It’s not normal for a car to experience a sudden decrease in fuel efficiency. Several components could cause worsening gas mileage, including:
  • Fuel injectors: The injectors have small nozzles which send fuel into the cylinders. Over time, they can become clogged. This can lead to slow acceleration and a drop in fuel efficiency. 
  • Tires: Misaligned tires can lead to a decrease in mileage. The mechanic may check the air pressure and realign the tires.
  • Fuel pump and filter: These are key components in your combustion system. If your fuel pump is bad, you won’t get enough fuel, leading to stalling and poor mileage.
  • Spark plugs: To burn fuel, your vehicle needs a spark. If the plugs are malfunctioning, the result could be rough idling and a huge decrease in fuel efficiency.
  • Oxygen sensor and mass airflow sensor: A dirty oxygen sensor may impact the amount of fuel entering the engine. If it is communicating an inaccurate number, you could experience a drop in MPG or a rough idle. 
  • Brake calipers: It’s rare, but sometimes a caliper gets stuck on a disc brake. This will seriously impact your mileage and make driving very dangerous.

How to get an inspection when your car is getting worse gas mileage

Your entire fuel system needs to be inspected to determine the source of the problem. Mechanics will inspect:  
  • Sensors and electronics
  • Fuel filter and pump
  • Spark plugs
  • And more
Call a garage and explain that your car is getting worse gas mileage. Describe any sounds you have been hearing if you can identify them. Ask for a fuel system and engine inspection. 

How long will an inspection take?

This inspection may take half a day or longer to rule out all potential sources of the problem. 

How do I know if I need to get an engine inspection when my car is getting worse gas mileage?

In addition to worse gas mileage, you may observe stalling or shuddering. Poor acceleration is a symptom of inefficient combustion, too. All of these signs justify getting an inspection. 

How important is a fuel system inspection

An unexpectedly inefficient engine is an indication that something is wrong with your car—and it could be dangerous. 
If it’s just a problem with a sensor, you’re not in serious danger. However, a problem with the spark plugs or a stuck caliper could be treacherous. At the first sign of decreasing mileage, book an appointment.