Toyota

Have Toyota Questions? Ask a Mechanic for Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Gas mileage drop off bad, time, 2007 prius, nothing will…

Customer Question
Gas mileage drop off...

Gas mileage drop off bad

Mechanic's Assistant: When did you last clean or replace your air filter? And are the oxygen sensors in good working order?

Long time

Mechanic's Assistant: What is the model/year of your Toyota?

2007 prius

Mechanic's Assistant: Are you fixing your Prius yourself? What have you tried so far?

Nothing will bring it to you

Submitted: 1 year ago.Category: Toyota
Show More
Show Less
Ask Your Own Toyota Question
Answered in 1 hour by:
12/14/2016
Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago
Matt
Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 23,309
Experience: BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years
Verified

Hello

This could be a number of things:

Incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

One other thing is to ensure that you're running on the correct grade of engine and gearbox oil as if its too thick or overfilled this will really hurt the fuel economy

Air leak at the mass airflow meter -

Any air dragged after the meter isn't 'seen' by the ECU and so not compensated for, causing rough running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Binding brakes:

Check that all the wheels can be turned freely by hand, and free off any sticking calipers

Incorrect wheel alignment:

Check all the tyres for signs of uneven wear if it has any then get it checked out at a place that does 4 wheel alignment not just front tracking and ensure tyres are pumped up to their recommended maximum

Injectors are clean and not dribbling - add a bottle of injector cleaner to the tank

Use good quality fuel - from my own findings its worth paying the extra for BP or shell as typically you'll get another 10% fuel saving which outweighs the cost over supermarket fuel.

Ask Your Own Toyota Question
Toyota Mechanic: Matt, Mechanical Engineer replied 1 year ago

Hi

do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Ask Your Own Toyota Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a toyota mechanicLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Matt Your Own Question
Matt
Matt
Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 23,309
23,309 Satisfied Customers
Experience: BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years

Matt is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

THANK YOU, THANK YOU, THANK YOU!! I've got my baby back. Tomorrow I will get a tank of high octane, remove the top, go for a long long ride and enjoy my car. THANK YOU!

JugheadUSA

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

< Previous | Next >

Meet the Experts:

Chris (aka-Moose)

Chris (aka-Moose)

Auto Technician

1,104 satisfied customers

16 years of experience

Marty

Marty

ASE Certified Technician

197 satisfied customers

ASE & Bosch Master Tech. 30 years experience.

Amedee

Amedee

Toyota Technician

1,243 satisfied customers

ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector

Anthony

Anthony

ASE Certified Technician

401 satisfied customers

ASE Master Automobile Technician with over 20 years exp. in this field.

Richard

Richard

ASE Certified Technician

9 satisfied customers

Toyota tech. ASE Certified Technician

Skyvisions

Skyvisions

ASE Certified Technician

13,051 satisfied customers

Toyota Master Diagnostic

Genchi Genbutsu

Genchi Genbutsu

Toyota Master Technician

3,761 satisfied customers

Toyota Certified Master Diagnostic Technician, ASE Master Technician with L1 Advanced Engine

< Previous | Next >

Related Toyota Questions
Gas or heavy exhaust smell in prius cabin while driving. Not
gas or heavy exhaust smell in prius cabin while driving … read more
heavy_chevy_396
heavy_chevy_396
Vocational, Technical or Trade Scho
2,518 satisfied customers
My granddaughter bought a 2005 Toyota Prius. I would like
My granddaughter bought a 2005 Toyota Prius. I would like one too. Problem is; the battery died after she had it only a few months. So would some Toyota technician or engineer engage with me for a bit… read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
Prius: 2007 Prius with 82,250 miles - seems it should be getting
2007 Prius with 82,250 miles - seems it should be getting better gas mileage. I bought it used when it had 42,000 miles and the dealer said it was getting 50 mpg city and 60 mpg hwy. My best mileage h… read more
toyotek01
toyotek01
297 satisfied customers
Prius: Is anything damaged when a prius is left running when
Is anything damaged when a prius is left running when parked for a long time? i ACCIDENTLY LEFT MY 2007 RUNNING WHEN PARKED AT THE AIRPORT FOR FOUR DAYS AND NOW MY MILEAGE HAS DECREASED TO 44MPG FROM … read more
toyotek01
toyotek01
297 satisfied customers
2007 Prius wont start. All the dash lights came on (and stayed
2007 Prius won't start. All the dash lights came on (and stayed on) but it won't start. I had to hold the power button for 10 seconds or so to turn off the car. I repeated these steps 3 or 4 more time… read more
Toyota Service
Toyota Service
Toyota Dealership Service & CR Manager
1,344 satisfied customers
Prius: I found an old post that talked about Prius mileage
I found an old post that talked about Prius mileage suddenly dropping. I had been consistently getting 40-45 mpg on my 2007 (bought new) and it suddenly dropped to 27-33 about 2-3 months ago. Same dri… read more
Toyota Service
Toyota Service
Toyota Dealership Service & CR Manager
1,344 satisfied customers
2007 Prius: Runs great...headlights occasionally go off by themselves
I have a 2007 Prius. Runs great. For past few months though have noticed that headlights occasionally go off by themselves. Right, left, seems random. Other lights seem to be working just fine. Pullin… read more
sfe30
sfe30
Master Technician
Vocational, Technical or Trade Scho
157 satisfied customers
2007 Toyota Prius: considering buying..with about 130k miles
Hello - I am considering buying a used 2007 Toyota Prius with about 130K miles on it from a dealer. Single owner on record as per the car fax. The car has been in one accident. The dealer said it was … read more
Dj
Dj
Auto Failure Analysis & Inspections
High School or GED
1,360 satisfied customers
2006 Prius: meter..put new..serviced..173,000km; the tires are good
I presume that to repair the combination meter in my 2006 Prius will run between$500 to $1000 as I deal with a small dealer and probably that have not done one before. I was going to trade knowing wha… read more
AMD
AMD
Master Automobile Technician
Vocational, Technical or Trade Scho
980 satisfied customers
prius: gas mileage has for 50,000 miles been from 42 to 48..overdrive
I have prius 2010 -- gas mileage has for 50,000 miles been from 42 to 48. last month I changed tires same size as original but mileage dropped to 37 to 42. I also feel at times it is like the overdriv… read more
Matt
Matt
Mechanical Engineer
Bachelor's Degree
23,309 satisfied customers
2005 Prius: this summer the millage seem to be worse than before
Hello I have a 2005 Prius, this summer the millage seem to be worse than before. I use to get 38 to 42 MPG. No i am getting only about 33MPG. I tend to think it is the hot summer driving that i am doi… read more
scionking
scionking
Toyota Master Certified
Associate Degree
237 satisfied customers
2005 Prius: about 49,000 miles and has received the check up.
Have a 2005 Prius bought in April. It now has about 49,000 miles and has received the check up. Was fine all summer. In Oct I moved some heavy stones about 3 miles. Next time I went to use the car the… read more
Genchi Genbutsu
Genchi Genbutsu
Toyota Master Technician
Vocational, Technical or Trade Scho
3,761 satisfied customers
toyota prius: 38 miles per gallon..that can be done to improve the mpg
I bought my Toyotal Prius new in May of 2007. Ever since I have had the car, it has never gotten better the 38 miles per gallon and never gets 40mpg or better. I am not a "lead foot" and wonder if the… read more
ToyotaTom
ToyotaTom
some college education
138 satisfied customers
2007 Toyota Prius: gas mileage has dropped from 49-50 mpg to 39-40 mpg
I have a 2007 Toyota Prius. It had to be jump started 3/13/10 and again 5/12/10. Since the first jump start, the gas mileage has dropped from 49-50 mpg to 39-40 mpg and also the bars on the display sc… read more
Toyotapro
Toyotapro
Technician
Vocational, Technical or Trade Scho
9,283 satisfied customers
Mileage indicator suddenly showing 10-14 mpg..restarted
Mileage indicator suddenly showing 10-14 mpg, down from 50 mpg. What happened? Have turned off and restarted engine several times.… read more
Boxer54
Boxer54
Line Technician
2 years university - did not gradua
1,563 satisfied customers
2007 Prius: gas mileage..serviced..oil change..tire rotaion
We have noticed a significant decrease in gas mileage in our 2007 Prius since it was last serviced a few weeks ago.....just a routine oil change, tire rotaion and thee was a engine filter changed. WE … read more
Jay Champagne
Jay Champagne
Team Leader
High School or GED
186 satisfied customers
2007 Toyota Prius: town..road..I step on the accelerator..high speed
I have recently purchased a used 2007 Toyota Prius. I find it is getting poor milage around town (below 40) and less than normal milage on the road (~42). I have a 2003 Prius and when I compare the op… read more
ted ritter
ted ritter
Team Leader/toyota master tech/retired
High School or GED
2,692 satisfied customers
Yaris: new car as my old one is dying..gas mileage..vehicles..mpg
I'm 65 yrs old and need a new car as my old one is dying. I like the look of the Yaris but wonder if I should consider Prius for even better gas mileage.Would like your expert opinion on both vehicles… read more
Skyvisions
Skyvisions
ASE Certified Technician
High School or GED
13,051 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x