Hi,

My Mazda CX-5 is getting poor gas mileage and I need help figuring out what wrong. I have done all the recalls on the SUV and thought the new fuel pump would fix things. I was getting 360 mile to empty . Now it is down to 315 mile to empty. Any suggestions on what I should do?
Thanks

 

What changed between the two values, like weather, type of driving, new tires, different drivers? Using a distance to “empty” is not a very exact way to calculate fuel usage, do you have actual mpg values? Were these values just single occurrences or averages? Tell us more about your CX, like trim and engine. It’s difficult to provide meaningful help without more information.

 

Gasoline expands and contracts according to the temperature.
Distance to empty is a nearly useless way to measure gas mileage.as it does not take into account that volume variability or anything else for that matter.
You need to write down your mileage and the number of gallons/liters when you fill your tank.
Then when get gasoline you need to write down the mileage and gallons and do the math.
This should be done at various intervals. Not just when you fill up.
You will also need to keep a record of who is driving, road and weather conditions and terrain the driving is done in.
Highway driving mileage varies greatly from city stop and go and hills and mountains.
And any changes that have been done on the vehicle since the last time you purchased any gas.

 

ROLMAO, dude that's funny ! BEST ADVISE and I know I could not have written the response as well!




Always use Chevron Supreme 93-95 octane, fuel tank rarely gets below 1/2 full and I know the actual certified weight of my Mazda.

 

I showed your post to my wife.
I'm not sure if I convinced her I'm not nuts or if she thinks you're as crazy as I am.
I've been keeping notebooks my entire life for just about everything from gas mileage to weather conditions when I go fishing/hunting.
I must say my MPG tracker on my 2020 CX-5 is pretty damn near spot on with my logbook every time.
So much so, that I'm thinking about not using a log...or maybe I'm just getting apathetic in my old age.

 

Mine as well, but I am a creature of habits with some things. Also, I log every service I do. I think this is the Diving and flying habits that carried over to vehicles?

 

Many things affect fuel mileage. A new set of tires can improve mileage or maybe hurt mileage. Tire pressure of course, I tend to run mine a few pounds over the
recommended pressures. I've had a car with a wheel bearing going bad. Checked OK when cold, got tight when a few miles (a trip) warmed it up. Also brake drag
could be a factor, not always obvious. How many miles on vehicle? Dirty air filter, dirty injectors, etc. can make a good size dent in mileage.
My 2¢

 

You think there is a reason why that recommendation is in the door jam of just about all cars worldwide and specifically required for any vehicle sold in the USA by the DOT?
This psi is always debated on forum., for me . its simple you are not track racing your vehicle so there is a reason why there is a service recommendation and most has to do with the best safe operation of you vehicle as it was designed.

But the rest of your response is pretty good. sorta....

 

Thank you everyone for the replies.

It is 2.5L Touring FWD, Sunroof, Bose system, and Power tailgate. It has with 42k miles. As for tire, it has with 19" Michelin - CrossClimate2 install Nov 2021. They have around 7k miles on them (i do need to get them rotated and balance). It is averaging 23.9 mpg and it is winter here. I changed the oil 1500 miles early to see if that was the issue along with the air filter in Dec 2022. (Mobil 1 0-20w 5 quarts Fram Tough Guard) As for service, the fuel pump was changed in Nov 2022, per recall, and I replaced 4 brakes Dec 2022. I use regular 87 and fill up when the SUV is near empty. I noticed "the problem" around Oct 2022 but thought the new fuel pump would fix "the problem".

Thanks.

 

The use of 87 octane can affect the MPG contrary to what is posted anywhere. It is simple physics if the engine does not produce a good level of Torque, then it takes more fuel (throttle) to get the vehicle moving and that translates to a slightly lower MPG. *The other thing before a few members starts jumping in to protest my information.... most people in the US and Canada do not check the fuel formulas they are using which can have a direct effect on the MPG. I might add that less than top tier gasoline like Chevron and Shell will not yield as much power which could reduce MPG.
Your decrease in MPG does not really look terribly out of line and there is not a 12-month record to actually determine the exact cause of your slight decrease in MPG.

* Mazda does not participate in certification standards when posting the power ratings of any model from at least 2014 and newer. The MPG is based on condition tested by Mazda which they do not post. The Mazda ECU calibration has slight adjustments from sensor information when using low octane fuels which directly effects the MPG.