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2019 Honda Civic Sdn - MPG change

I have a 2019 Honda Civic and have been leasing them for a long time. It is a great car for the money and gets great gas mileage. I know this because the miles per gallon is displayed near the odometer. I took it into the dealership for routine service including oil change, tire rotation, and asked if they could determine the noise I hear from the driver side wheel. The mpg when I took the car in was about 38. When I got it back, about two hours later, the mpg reading was around 34. I did not check the odometer reading but know they took the car out to listen for the noise. Even so, the mpg should not have changed that dramatically. Can you speculate what could have cause this?

No but you realize these are not NASA grade instruments . Are you not resetting the dash readouts at each fill up ? And are your checking your miles per gallon with pen and paper to see just how close the read outs are ?
One of my vehicles on the highway the readout is really close but in town only driving it is about 2 miles per gallon higher than actual .
Frankly you should be more concerned about the noise then the read out.

Cars typically get poor fuel economy in parking lots, in the shop, on short road tests and in the car wash. Your fuel economy display is showing the change in driving environment.


Frankly I haven’t even looked at the MPG display on my car in years. Whenever I stop for gas I calculate my mileage the old fashioned way. It dropped a bit when I had the tires replaced with a different brand but that’s not terribly uncommon.

It is not unusual for me to take my car for service with the MPG display reading 24 or even 25 mpg, but when I pick it up, the reading is something on the order of 20 mpg. Between low-speed shuttling of the vehicle from the lot to the shop, and then shuttling it to various positions in the shop, plus idling in the shop, and then (most likely) some lead-footed behavior on the part of the mechanic when he does the post-service test drive, the mileage is bound to plummet.

My suggestion for the OP is as follows:
Refill your gas tank, zero-out your trip odometer, and see what type of mpg reading you get before the next fill-up. As long as you can attain your previous level of fuel economy, then there is no problem.

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34 versus 38 is not too drastic of a change, at least in my experience. There are so many variables like the weather and time of day can affect your mileage.

That said it’s possible you might have a dirty air filter?

Doubtful if a 2019 has a really dirty air filter and that does not make any difference with fuel injection like it did for carburetor vehicles of years ago.

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I disagree, your car needs air. The oxygen burnt in the air fuel mixture is part of your fuel source and that comes from the atmosphere. A dirty filter absolutely will affect this guaranteed. I’m 99% certain it might even mention this in the Honda owners manuel.

Very unlikely it’s an air filter problem on a near new car. The mags haven’t been measured very consistently.

Modern computer controlled engines reduce the fuel supplied to the cylinders if the air supply gets reduced by, say, and clogged air filter. That way excess emissions are prevented.

I asked Manuel and Pedro, and they both advised that I read the manual.


the guy test driving the car probably had a heavy foot and with these cars using the wonderful CVT’s they take awhile to get into the efficient range so if he had his foot into it to get it to go which it usually does take an higher throttle input to get it moving it could have easily lowered the reading on the trip odometer .

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Even carbureted engines are not much affected by air filter restriction.