Q: The car has a decrease in gas mileage

asked by on August 04, 2016

I have a well-maintained car that has been running great with no major problems. Except for the poor gas mileage issue, for which I went to the dealership but was told that nothing is wrong. This problem started occuring several months ago. Up to now, the miles per gallon decreased 23% and I would like to know why. I haven't changed anything in my driving habits so this is very unusal. What could cause this? What can I do to improve gas mileage?

Oxygen Sensor Replacement $123.80 - $932.74 Get a Quote
Car is getting worse gas mileage Inspection $94.99 - $114.99 Get a Quote

Hello. For a sudden drop like this to occur, it usually means that a sensor it not reading correctly. I usually install a scan tool first to check things like the oxygen sensors and the air flow meter as they are the most common causes of a drop in MPG. If nothing is found, then I clean out the air flow meter and reset the computer and that usually takes care of it. If you need to have this checked, consider YourMechanic, as a certified mechanic can come to your home or office to inspect your fuel system and let you if any adjustments or repairs should be made. It is possible that the decrease in MPG could merely be a result of a change in recent driving habits.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

High idling happening occasionally after driving over 8 miles
Hi there. Most of the time this is caused by a problem with the throttle body (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-throttle-body). I usually clean it out first and inspect it for wear. If there is wear around the throttle plate then it needs to...
Engine runs at 4000 rpms shuts off get a P2074 code
There is a technical service bulletin 18-007-08 that covers this code and calls for a reprogram of the PCM to fix the issue. You should have the reprogramming done first before replacing any parts for this code. The P2074 code...
Can a defective catalytic converter cause clutch failure?
To answer your question, a catalytic converter cannot cause clutch failure. You have a series of independent failures, which is not very common for vehicles with less than 100,000 miles. I would take your 2013 Chevrolet Cruze back to the...
Stuck brake caliper
Although it is possible for a collapsed (internally and thus "invisible") rubber brake line to cause a retraction failure, by far the most common scenario is the caliper is sticking. If the calipers have more than, say, 70,000 miles on...
Transmission fluid is leaking out and the speedometer is not working.
Many common faults will cause your 1997 Ford F-150 to have a transmission leak and a speedometer that does not function. Transmission leaks can occur in various areas but the most common are the pan gasket, output seal, sensor seals,...
Car is not firing on the first two cylinders
This is generally related to spark problems when it is more consistent. Spark related problems generally will result from things like ignition coils, crankshaft position sensor, spark plugs, spark plug wires or ignition modules not working properly. As you know,...
Where is ecm relay located 2008 impala lt
All fuses and relays in the vehicle will be located in the fuse box or power distribution box. The fuse box is usually located inside the vehicle or sometimes in the trunk. The most common spot for this relay to...
starter switch replaced and do you have the computer to reset it. Also need help to put my new gas tank in. I have taken all bolts
Hello. After replacing the ignition switch on your vehicle you should be able to reprogram it manually. Putting the key into the ignition and leaving it there for a few seconds until an indicator comes up on the dashboard saying...
How much cost could be to replace a timing cover gasket on 2011 hyundai sonata 4cly? And the working time expectation?
Hi there. If the gasket in between the timing cover and the engine is leaking, it is recommended to replace the timing cover and gasket at the same time. In many cases, when the gasket becomes damaged, the cover itself...

Related articles

The Most Common Error Codes for Transmission Problems
If your Check Engine Light has come on, there are a number of conditions that could be causing it. Many are related...
Audi Certified Pre-Owned (CPO) Car Program
If If you’re looking for a used Audi vehicle, you may want to check out their certified pre-owned program. Many manufacturers have a certified pre-owned (CPO) program, and each one is set up differently. Read on to learn about the...
The Best Tool to Diagnose Sensor Failures
Mechanics may regularly run into sensor failures when performing a repair service. Automotive oscilloscopes help properly diagnose these issues.