Skip the auto shop - Our mechanics make house calls

Q: Car gets very low gas mileage

asked by on

The car has been getting a very bad gas mileage. When I bought the car, I figured that the data on the dash need some mileage to provide accurate data. I checked the MPG manually and I've been getting around 20 on the highway, which should be up to 29 MPG for this make and model. Moreover, when I drive in the city traffic, I've been getting around 18 MPG, which again should be up to 24 MPG. That is a big difference. As for my driving style, I'm keen on acceleration but I don't drive violently so that cannot be the cause. At the dealership, they didn't get any error codes so they couldn't help me. They only told me that it might be caused by my installing the bike roof rack. But that is the Mazda OEM part and in any case, I had bad gas mileage even before I had that installed. Lately, I've been measuring the MPG both with the meter on the dashboard and manually and the data shown is accurate. Do you have some suggestion on how I could improve this horrible gas mileage? Is there any part that has gone bad that causes this?

A: I would do a little quick research and find...

I would do a little quick research and find out what is typical real-world MPG for others who drive your make and model. That will provide you a realistic base-line expectation that will be more accurate that Mazda or EPA estimates. Now to a few things that can hurt fuel mileage. The wind resistance from the rack will certainly make a difference. But more at highways speeds and less so around town at lower speeds. Tire inflation is a factor. Check them monthly and inflate as per door sticker. Your right foot is probably the biggest variable in all of this.

You could do an experiment! For one week drive like there is an egg between your right foot and the gas pedal. Your mission is to press very gently on the pedal so you don't break the egg! The results will indicate if your poor gas mileage is due to "enthusiastic" driving. I don't know if your Mazda has an automatic or manual transmission. If you have a stick shift and you regularly run it up to higher rpm's before shifting, that will use more gas. If I was looking at scan tool data for an engine performance problem that was hurting gas mileage, I would view fuel trims and misfire data after checking for diagnostic trouble codes (DTC's). If you would like to have this checked, a certified technician from YourMechanic can come to your home or office to diagnose the mileage issue.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Warning lights came on, and I received code P0442 and the gas cap appears to be broken

A P0442 fault indicates a leak in the evaporative emissions system, or EVAP system for short. You are already on the correct path by checking the gas cap first. This is the most common reason for this fault, though it...

Q: 2010 Chevrolet Equinox not moving in reverse

Having a vehicle that will not move when it is shifted can be a frustrating experience. Due to the information provided being very limited, it is difficult to narrow down exactly the cause to the Equinox not going in reverse....

Q: Putting K&N short ram intake in a 2011 Mazda 3 Sport

First, I wouldn't recommend adding a short ram intake. Race cars have those short ram intakes on them, but they are programed by professional mechanics who use dynamometers and 5 gas analyzers to make the car run as efficiently as...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.