# Sudden MPG drop **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** corolla, toyota\ **Created:** [March 31, 2013, 11:40pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380 "2013-03-31T23:40:08Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![liviaoneday](https://avatars.discourse-cdn.com/v4/letter/l/d78d45/32.png) [@liviaoneday](https://community.cartalk.com/u/liviaoneday)\ **Post date:** [March 31, 2013, 11:40pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/1 "2013-03-31T23:40:08Z")
My 2000 corolla has consistently gotten35 MPG until last month, suddenly I’ve dropped to 18-20 miles per gallon, a friend suggested fuel filter fail, but i can’t discern if it has an external one ---
**Author:** ![dagosa](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dagosa/32/9837_2.png) [@dagosa](https://community.cartalk.com/u/dagosa)\ **Post date:** [March 31, 2013, 11:47pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/2 "2013-03-31T23:47:34Z")
Earlier then 2001 may be at the fuel tank. I would encourage that to be done by a mechanic at a garage if it is. It may need a tune up in general including air filter and inspection of vacuum lines, dragging brakes etc. which I would suspect too. When was that last done ? ---
**Author:** ![Proac\_fan](https://avatars.discourse-cdn.com/v4/letter/p/58f4c7/32.png) [@Proac\_fan](https://community.cartalk.com/u/Proac_fan)\ **Post date:** [March 31, 2013, 11:47pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/3 "2013-03-31T23:47:36Z")
It certainly does have an external fuel filter but I’d be more inclined to look for a faulty O2 sensor first. ---
**Author:** ![common-sense-answer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/common-sense-answer/32/716_2.png) [@common-sense-answer](https://community.cartalk.com/u/common-sense-answer)\ **Post date:** [March 31, 2013, 11:49pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/4 "2013-03-31T23:49:43Z")
**_I Believe That If A “Fuel Filter Fail” Caused That Kind Of Decrease In MPG That You’d Smell Gasoline And You’d Be Slipping And Falling In The Stuff._** Has the sudden drop in mpg been accompanied by any performance issues (rough running, idling, stalling, stumbling/missing, smoke, etcetera) or has the “Check Engine Light” illuminated ? What procedure do you employ to check your mpg ? Is that an average over several fill-ups ? _ **CSA** _ ---
**Author:** ![liviaoneday](https://avatars.discourse-cdn.com/v4/letter/l/d78d45/32.png) [@liviaoneday](https://community.cartalk.com/u/liviaoneday)\ **Post date:** [April 1, 2013, 12:07am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/5 "2013-04-01T00:07:34Z")
amazed and grateful at getting a response so quickly, I reset my trip-ometer and rarely do I not fill-er up so its very easy to keep track of mileage, I haven’t noticed any other problems associated w/ this sudden drop. I’ve had the car 10 years and am always pleased to see what great mileage and overall good performance ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [April 1, 2013, 12:19am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/6 "2013-04-01T00:19:17Z")
In addition to the other suggestions, you might also have a bad MAP sensor or ECT sensor. Those two sensors also have an effect on fuel economy. ---
**Author:** ![dagosa](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dagosa/32/9837_2.png) [@dagosa](https://community.cartalk.com/u/dagosa)\ **Post date:** [April 1, 2013, 1:00am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/7 "2013-04-01T01:00:19Z")
@proactfan [http://www.bing.com/images/search?q=2000+corolla+fuel+filter+location.&qpvt=2000+corolla+fuel+filter+location.&FORM=IGRE](http://www.bing.com/images/search?q=2000+corolla+fuel+filter+location.&qpvt=2000+corolla+fuel+filter+location.&FORM=IGRE) Hence the word may and if…wasn’t sure…notice " at "not in . ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [April 1, 2013, 2:16am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/8 "2013-04-01T02:16:43Z")
Add a stuck thermostat to the list of suspects. ---
**Author:** ![liviaoneday](https://avatars.discourse-cdn.com/v4/letter/l/d78d45/32.png) [@liviaoneday](https://community.cartalk.com/u/liviaoneday)\ **Post date:** [April 1, 2013, 3:09am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/9 "2013-04-01T03:09:58Z")
thanks, I heard just a snippet about that on a recent episode ---
**Author:** ![shannon\_darst](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/shannon_darst/32/2606_2.png) [@shannon\_darst](https://community.cartalk.com/u/shannon_darst)\ **Post date:** [April 1, 2013, 6:30am UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/10 "2013-04-01T06:30:39Z")
check you air filter ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [April 1, 2013, 10:51pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/11 "2013-04-01T22:51:17Z")
The guv’ment sez air filters have little effect on MPG: > **[Air\_Filter\_Effects\_02\_26\_2009.pdf](https://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf)** > > 1045.67 KB ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [April 1, 2013, 11:56pm UTC](https://community.cartalk.com/t/sudden-mpg-drop/78380/12 "2013-04-01T23:56:04Z")
How many miles does the car have on it? When was the last time you had the sparkplugs changed? What brand did you use? Have there been any other operating problems? If you plan to work on the car yourself, a repair manual will be invaluable. They’re availebl over the internet or at your local parts store.