# Worst Gas Mileage after battery change

**URL:** <https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170>\
**Category:** Power/Fuel\
**Tags:** hyundai, sonata\
**Created:** [October 13, 2020, 3:16pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170 "2020-10-13T15:16:38Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![MilindaRanawaka](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/milindaranawaka/32/22869_2.png) [@MilindaRanawaka](https://community.cartalk.com/u/MilindaRanawaka)\
**Post date:** [October 13, 2020, 3:16pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170/1 "2020-10-13T15:16:39Z")

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Hey,

I have a 2001 Hyundai Sonata. I change the car batter myself. After change the battery I drove like 50KM. I notice I got the worst gas mileage ever. Now it’s getting an average like 2-3Km from a petrol liter. I got an average 10Km from a petrol liter. Is there any reset I should have done after putting a new battery?

Thank you.

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**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\
**Post date:** [October 13, 2020, 3:21pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170/2 "2020-10-13T15:21:16Z")

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> [@MilindaRanawaka](#):
>
> Is there any reset I should have done after putting a new battery

No, you DID the reset by replacing the battery… I suspect you are using the car’s mileage calculations to determine your fuel use. THAT is what got reset and it takes a little while to properly update the actual mileage. It also resets the “learned” values for the engine and that can reduce mileage for a little bit until the cars computer “learns” your engine again.

You don’t need to do anything but be patient.

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**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\
**Post date:** [October 13, 2020, 3:42pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170/3 "2020-10-13T15:42:50Z")

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Do you not reset the read out each time you fill the fuel tank . Changing the battery does the same thing . You need to reset the ( MPG-AVG speed - Trip Odometer ) and that will give you a better idea of your actual fuel usage for the type of driving you did on each time.

Also check your fuel usage the old fashioned way once in a while to see just how accurate the read outs are.

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**Author:** ![lion9car](https://avatars.discourse-cdn.com/v4/letter/l/59ef9b/32.png) [@lion9car](https://community.cartalk.com/u/lion9car)\
**Post date:** [October 13, 2020, 5:52pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170/4 "2020-10-13T17:52:32Z")

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Is your check-engine light on? Does your car smell like gas (petrol) or rotten eggs after you drive it?

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**Author:** ![COROLLAGUY1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/corollaguy1/32/7575_2.png) [@COROLLAGUY1](https://community.cartalk.com/u/COROLLAGUY1)\
**Post date:** [October 13, 2020, 6:54pm UTC](https://community.cartalk.com/t/worst-gas-mileage-after-battery-change/171170/5 "2020-10-13T18:54:29Z")

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You could have knocked out some other parts while doing the battery change.Did you remove anything else that was in the way to take out the battery? On mine I have to remove parts of the airbox assembly to gain access to the battery