1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Worse gas mileage in 2010 Prius after fuel system cleaner

Discussion in 'Gen 3 Prius Fuel Economy' started by Noahlang94, Feb 10, 2024.

Tags:
  1. Noahlang94

    Noahlang94 New Member

    Joined:
    Feb 10, 2024
    5
    3
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    Three
    I bought a 2010 prius used at 163k. When I bought it, I was getting 49+ mpg. Eventually though, it started dropping. Since I bought it, I’ve done all oil changes myself using Mobil 1 oil and have been trying to take good care of it. I have access to most service history and it was taken care of at the shop for mostly everything. Any way, I was kinda curious if fuel injector cleaner could help, so I got some Lucas cleaner and ran a couple bottles of that through separately. I think the first bottle made the mpg drop down about 8-10 miles per gallon, then the second bottle made it drop even more. Yesterday I decided to try that chevron Techron cleaner and I noticed it’s starting to drop more again. Problably 10k miles ago I changed out the spark plugs and decided to go with Ngk iridium’s. At this point I mean I don’t know what to do. Right now I’m sitting around 38mpg.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    108,235
    49,204
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    idk, but google has a lot of thoughts. maybe just drive it for awhile and see if it improves. possibly check the plugs for fouling., clean the throttle body.
    have you cleaned the egr circuit?
     
    Noahlang94 and Mendel Leisk like this.
  3. Brian1954

    Brian1954 Active Member

    Joined:
    Jan 31, 2021
    720
    270
    0
    Location:
    South Central PA, USA
    Vehicle:
    2011 Prius
    Model:
    III
    How many miles are on the car now?

    What percentage of your driving is city vs. highway?

    Have you purchased new tires?

    How old is your 12v battery?

    From my experience, my winter fuel mileage is 8 MPG lower than in the summer.

    Check for brake drag by elevating the car and spinning the wheels.

    Maybe your HV battery is losing capacity, and your fuel mileage is dropping because of it.
     
    Noahlang94 likes this.
  4. Mendel Leisk

    Mendel Leisk Luddite

    Joined:
    Oct 17, 2010
    55,106
    38,467
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Second this, well overdue. Should be done by 100k at the latest, then every 50k thereafter. Intake manifold is part of the EGR system, should be cleaned as well.

    see first two links in my signature; on a phone turn it landscape to see signature.

    FWIW, with 3rd gens for sale with that kind of mileage, there’s a good chance previous owner was ditching it due to head gasket letting go, possibly masked with a stop-leak product.
     
    Noahlang94 likes this.
  5. nicoj36

    nicoj36 Active Member

    Joined:
    Oct 15, 2013
    495
    157
    0
    Vehicle:
    2010 Prius
    Model:
    II


    clean the maf sensor with crc, do a redline fuel treatment, and do this reset.
     
    Noahlang94 likes this.
  6. Noahlang94

    Noahlang94 New Member

    Joined:
    Feb 10, 2024
    5
    3
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    Three
    I have not cleaned out the egr circuit. I’ve done some digging on this before and I can have a coworker try to do that. I work at a car shop, and that’s a little more than I am capable of doing.
     
    mikey_t and bisco like this.
  7. Noahlang94

    Noahlang94 New Member

    Joined:
    Feb 10, 2024
    5
    3
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    Three
    thank you for the advice! Right now, it has I believe 185k. Mostly city now, but I do a decent amount of highway. I did have winter tires on it that I’ll pull off here in about a month or so. As for the 12v battery, I have no clue. I can check the battery and the brakes at work one of these days! As for the hybrid battery, that was my fear. I’ll try these other tips though before I freak out over the battery! Thank you!
     
    mikey_t likes this.