What Causes A Decrease In Fuel Efficiency?

A sudden decrease in fuel efficiency can be alarming, especially if your heart is set on a planned road trip. While a reduction in fuel efficiency can be a result of some minor issues, sometimes it can be an indicator of a more severe problem. If ignored, you can expect to deal with some mechanical issues that develop into costly repairs. While many factors can lead to an increase in fuel consumption, below are some of the most common factors: 

Oxygen Sensor

Your vehicle’s oxygen sensor measures exactly how rich or lean your exhaust gases are when they leave the combustion chamber. A dirty or failing oxygen sensor can lead to a significant drop-in mile per gallon by up to 20 percent. A faulty oxygen sensor can also lead to your vehicle idling rough and a failed emission test. 


If your vehicle carries a lot of weight, it can lead to an increase in fuel consumption. The weight can consist of too many passengers, items, or roof cargo. The heavier the weight your vehicle is carrying, the more power your engine needs to drive.  

You are driving with a lead foot

When you step hard on the accelerator, your vehicle’s throttle plate opens up. This allows more air to enter into its combustion chamber. Your car’s Engine Control Unit will respond by injecting more fuel. The simplest solution for this is to accelerate gradually. 

Bad Spark Plugs

The spark plugs ignite the fuel inside the combustion chamber, and if they aren’t working correctly, the engine can misfire. This can lead to poor engine performance, lack of power, and a decrease in fuel efficiency.

Air conditioner 

It’s summertime, so the air conditioner is going to be cranked up high. Unfortunately, the air conditioner puts more stress on your engine and leads to your vehicle burning more fuel. Consider using just the fan when driving at slower speeds. 

Tire pressure and alignment 

If your tires have low air pressure or are out of alignment, your vehicle can suffer a massive decrease in fuel efficiency. Tire pressure is an easy fix; you can properly inflate your tires on your next trip to the gas station. If you suspect your tires are out of alignment, don’t hesitate to bring your vehicle in for a service.  

Gas prices are high, why not get the best fuel economy your vehicle has to offer. If you notice a decrease in fuel performance, now is the best time to have your car inspected by Luke's Auto. Our inspection will help find the gas-guzzling culprit to help save you money in the long run.