# Large drop in gas mileage **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [January 14, 2024, 1:04am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164 "2024-01-14T01:04:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Andy-Ke](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/andy-ke/32/41664_2.png) [@Andy-Ke](https://community.cartalk.com/u/Andy-Ke)\ **Post date:** [January 14, 2024, 1:04am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/1 "2024-01-14T01:04:44Z")
I moved from a relatively flat area (Houston) to Central Texas close to Austin. My gas mileage has dropped from 20 mpg to around 16 mpg. I would like to find out why. I have a 2009 Mazda CX-7, The engine is running fine. I do live in a very hilly area. Thanks. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [January 14, 2024, 1:36am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/2 "2024-01-14T01:36:53Z")
[Fueleconomy.gov](http://Fueleconomy.gov) shows that the gas mileage for CX-7 2WD is 17 city, 23 highway and averages 20. The AWD version is 16 city, 22 highway and 18 average. Is your CX-7 AWD or 2WD? Also, some areas of the country reformulate gasoline during the winter and gas mileage drops around 10%. Still, hills may be a part of it. When I was still working I got better gas mileage going to work than going home, even when traffic was comparable. I decided that I was going uphill on the way home. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [January 14, 2024, 2:05am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/3 "2024-01-14T02:05:45Z")
Yep, hills will make you use more gas to go up them vs being on a flat road… ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [January 14, 2024, 3:57am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/4 "2024-01-14T03:57:04Z")
It’s gotten colder-have you checked your tires? ---
**Author:** ![ledhed75](https://avatars.discourse-cdn.com/v4/letter/l/f6c823/32.png) [@ledhed75](https://community.cartalk.com/u/ledhed75)\ **Post date:** [January 14, 2024, 12:32pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/5 "2024-01-14T12:32:27Z")
Are you doing more in-town driving, vs. highway? I’m familiar with the Austin area; there are a lot more hills than in the Houston area. That may be it. ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [January 14, 2024, 1:17pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/6 "2024-01-14T13:17:21Z")
I too suspect driving conditions, hills. In addition to above comment, have you had your cooling system serviced? Thermostat may be opening at a lower temperature, engine not getting up to proper temperature, but warm enough to not to set a fault code. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [January 14, 2024, 2:22pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/7 "2024-01-14T14:22:28Z")
Servicing cooling system means what? Changing coolant alone? Changing thermostat also? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 14, 2024, 2:39pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/8 "2024-01-14T14:39:54Z")
There have been several good suggestions for the OP, but I want to add a couple of other possibilities: Is the OP still carrying around anything from the recent move in his vehicle? Excess weight will take a toll on gas mileage, just as with low tire pressure, lower temperatures, and having to climb hills. Now that temps have dropped, is the OP “warming up” his engine before driving? With modern vehicles, warming-up is not necessary and it will definitely waste gas while the engine is in fast-idle mode. Simply start the engine and then drive conservatively for a few minutes until the engine warms-up. ---
**Author:** ![Andy-Ke](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/andy-ke/32/41664_2.png) [@Andy-Ke](https://community.cartalk.com/u/Andy-Ke)\ **Post date:** [January 14, 2024, 2:52pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/9 "2024-01-14T14:52:31Z")
I have no extra weight in my car. I do not warm up more than 1 minute. ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [January 14, 2024, 6:07pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/10 "2024-01-14T18:07:27Z")
Both, but thermostat is only changed if **not** working properly. If you read my comment, thermostat may be opening too soon, engine running too cold. “ Thermostat may be opening at a lower temperature” ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [January 14, 2024, 10:23pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/11 "2024-01-14T22:23:47Z")
My guess, the OP’s driving style has changed as a result of the move. Driving more shorter distances, slower, uphill, against the wind, etc. MPG will suffer from any deviation from driving a steady 60 mph on a no-wind day & level ground. The most important engine-factor for mpg is the coolant temperature. Too low will result in reduced mpg. So good idea to make sure the coolant is reaching the proper engine-warm-temperature quickly after starting the engine. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 14, 2024, 11:57pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/12 "2024-01-14T23:57:32Z")
> [@George\_San\_Jose1](#): > > against the wind +1 Today, the wind was gusting up to 50 mph in this area. I was driving my friend’s Forester, and when I began driving it was registering 25 mpg. As I usually can do with his car, w/in ~30 minutes, it was registering a hair over 30 mpg. However, then the wind really began to blow and push the car around. After about 30 minutes I witnessed the gas mileage drop by more than 1 mpg even though my speed was the same and I wasn’t driving on an upgrade. I believe that driving against the wind has to be the explanation. ---
**Author:** ![Andy-Ke](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/andy-ke/32/41664_2.png) [@Andy-Ke](https://community.cartalk.com/u/Andy-Ke)\ **Post date:** [January 17, 2024, 10:21pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/13 "2024-01-17T22:21:50Z")
Someone suggested that I check my tire pressure. My tires were around 20 - 22 psi. Well below the recommended presure of 32 p.s.i. I brought the tires up to 32 p.s.i. ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [January 17, 2024, 10:33pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/14 "2024-01-17T22:33:04Z")
Yes. You should check your tire pressures at minimum once a week, and certainly before taking a trip. Check them cold in the morning-ish. This is for more reasons than just fuel economy - like for safety. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [January 18, 2024, 2:45am UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/15 "2024-01-18T02:45:00Z")
> [@Andy-Ke](#): > > My tires were around 20 - 22 psi. Was the TPMS light not on, and an indication to check your tire air pressures?? My guess is they didn’t suddenly drop from 32 psi to 20 - 22 psi as soon as you moved, but it should help some, but remember, hills cause you to depress the gas pedal further to retain the same speed as on the flat area… ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 18, 2024, 1:59pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/16 "2024-01-18T13:59:10Z")
> [@davesmopar](#): > > Was the TPMS light not on, and an indication to check your tire air pressures?? Clearly, either the TPMS is not working, or the OP has been ignoring that light for… probably… a long time. He’s lucky that he didn’t wind-up with a blow-out from excessive flexing of the sidewalls at expressway speeds. > [@Andy-Ke](#): > > My tires were around 20 - 22 psi. > Well below the recommended presure of 32 p.s.i. Did you _not_ notice that the car’s handling/cornering ability had become badly degraded? ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [January 18, 2024, 3:28pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/17 "2024-01-18T15:28:20Z")
It may be related to the cold snap across the country, including parts of Texas where it rarely gets cold. That would cause tire pressure to drop quickly. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 18, 2024, 4:21pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/18 "2024-01-18T16:21:51Z")
> [@jtsanders](#): > > It may be related to the cold snap across the country, including parts of Texas where it rarely gets cold. That would cause tire pressure to drop quickly. Yes, but has the ambient temperature dropped by 100 degrees? If we accept that every 10 degree drop in temperature leads to the loss of 1 psi in tires, the loss of 10-12 psi would require a drop of at least 100 degrees. ---
**Author:** ![Rainflurry](https://avatars.discourse-cdn.com/v4/letter/r/cab0a1/32.png) [@Rainflurry](https://community.cartalk.com/u/Rainflurry)\ **Post date:** [January 18, 2024, 4:47pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/19 "2024-01-18T16:47:57Z")
Here is an interesting study by researchers at Oak Ridge National Lab: [https://www.energy.gov/eere/vehicles/fact-826-june-23-2014-effect-tire-pressure-fuel-economy](https://www.energy.gov/eere/vehicles/fact-826-june-23-2014-effect-tire-pressure-fuel-economy) According to the study, low tire pressure of this magnitude (~65% of recommended) reduces fuel economy by ~8% at 40 mph and by ~5% at 80 mph. The study didn’t look at speeds below 40 mph. The study was based on a 2009 Toyota Corolla. ---
**Author:** ![Andy-Ke](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/andy-ke/32/41664_2.png) [@Andy-Ke](https://community.cartalk.com/u/Andy-Ke)\ **Post date:** [January 18, 2024, 5:04pm UTC](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164/20 "2024-01-18T17:04:20Z")
The TPMS light only comes on when the tires are below around 25 p.s.i. I wish they came on sooner. [Next page](https://community.cartalk.com/t/large-drop-in-gas-mileage/194164.md?page=2)