2008 Prius bad mileage

Discussion in 'Gen 2 Prius Fuel Economy' started by Moepaq, Jun 9, 2021.

  1. Moepaq

    Moepaq New Member

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    My fuel economy is bad. I just bought a 2008 Prius with 225k miles on it. It has always been taken care of. Everything is good on it and both batteries are healthy. I'm getting 37 mpg average. The air filter, engine filter are good. I tried airing up the tires to what many recommended, so I'm trying 42 on the fronts and 40 on the rears.

    What else can I do to raise the mpg. Or since it's an older vehicle with that many miles, it won't be able to?

    Posted via the PriusChat mobile app.
     
  2. dolj

    dolj Senior Member

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    Lift the car off the ground and check each wheel turns freely and smoothly.

    Is this your first Prius or have you had previous experience driving a Prius?
     
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  3. bisco

    bisco cookie crumbler

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    what tires are you running? how do you know the health of the hybrid battery?

    how many miles are your trips? how much a/c are you using?
     
  4. bisco

    bisco cookie crumbler

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    welcome!

    what is your driving style?
     
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    What brand and model tires are on the car? If they aren't something that's Low Rolling Resistance then it can make a noticeable difference.

    Posted via the PriusChat mobile app.
     
  6. caliwaves

    caliwaves Junior Member

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    @Moepaq the spark plugs on my 2008, purchased at 169k miles, were never replaced; after i replaced it, it went from 41mpg to 45-47 mpg; 70/30 highway:city
     
  7. JoeB

    JoeB New Member

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    Start with the basics:
    1. Deal with basic roll resistance:
    • Set your tire pressures to 35 lbs.
    • Buy low roll resistance tires. (No, General Tire cheapos will not get good mileage.)
    2. Deal with air flow and measurement:
    • Install a new air filter,
    • clean your throttle body, and
    • inspect your MAF sensor.
    Here are some tips.
    • Make sure the filter is seated properly. (I speak from the school of hard knocks here--it is easy to get wrong.)
    • Inspect the MAF sensor connector for green crusties.
    • Make sure the filter housing is properly attached to the throttle body. There is a round metal band that must be loosened to remove it, and tightened when installing--many people neglect it. The engineers put it there for a reason.
    3. Deal with getting good, clean spark. This means:
    • Change the spark plugs, and regardless of what is in the car, or what you read out there in wizardland, put new, stock, original plugs in.
    • Inspect the coils. Check for green crusties on the connectors. Check for carbon tracks on the boots.
    • Check for oil in the spark plug tubes (there should be none).
    4. Deal with what it takes to get good clean 12 volt current on an old car:
    • If your 12 v battery is over 4 years old, replace it. There are (a few) healthy five year old 12 volt batteries--I owned one that lasted 7 years on a Corolla--but they are rare. Don't kid yourself and start with a known good situation.
    • clean the 12 v battery terminals very well. Inspect the wiring for crusties.
    • Clean the ground on the body where the negative battery post cable from the 12 v battery connects to the body.
    • Clean the engine ground strap. Where is it? Open the hood, face the back of the car, find the air cleaner. The wire on your left, running from the body near the radiator cap to the engine to a bolt near the left spark plug is the engine ground strap. It needs to be inspected for green crusties, and both ends must be removed and cleaned to get bright metal for all connections and then reattached.
    5. Install a new water pump belt. A stiff old one will not help your MPG cause, and a broken one will likely ruin your engine.
    6. Clean your VVT solinoid and filter. If your engine cannot set its intake valve timing, it will have poor gas mileage.
    7. Buy good quality gas, not the cheapest you can find.
    8. Clean your PCV valve.
     
    #7 JoeB, Jul 29, 2021
    Last edited: Jul 29, 2021
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  8. bisco

    bisco cookie crumbler

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    one hit wonder, 7 weeks ago...
     
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  9. Kaptainkid1

    Kaptainkid1 Active Member

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    My mileage is consistently bad because I drove my Prius under 5-10 miles at a time. I got 37 mpg as well because I had my AC on all time and drove under 5 miles for 90% of my commute and errands. If you drive over 10 miles per commute I think you could get 41 mpg and if you drove with the AC off I think you can get 44 mpg. My over mpg improved when I drove on the highway and not over 65 mph over 10 miles at a time. The engine needs to warm up and short drives kills the mpg on all Priis.

    Android ?
     
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  10. Another

    Another Active Member

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    Under 5 miles? Get a bicycle.
     
  11. ttou68

    ttou68 Active Member

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    I would definitely check the brakes to make sure the calipers and pads are free from rotors... Easiest way is to jack up the tires from ground and see if spin freely...

    Posted via the PriusChat mobile app.
     
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  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    There's valid reasons for short trips, grocery runs for example. And 5 miles is getting up there.
     
  13. Another

    Another Active Member

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    And of course going to a Starbucks is easier via car than bike. Bikes are underrated.
     
  14. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I hear you there. We’re blessed to be walking distance to a lot of amenities, Starbucks included), and when we’ve walked there with our Shiba, it’s dismaying, to see the snaking horseshoe that is the drive-thru clients, mostly CUV/SUV, inching along, virtually all the drivers looking down at some glowing object in their laps.

    One time, sitting with our Grande-sized honey/citrus/mint tea (we share it), I started postulating: to approach the city, propose to change the name, Coquitlam, to Drivethruville.

    still, our limits a km or two. A multiple stop shopping trip, 3~4 km distant, with heavy items: you gotta drive. We do try to consolidate trips when practical: say do that short shopping trip on the tail end of a cross-town run.

    And once in a long while, especially going downtown (where parking is nuts), we’ll leave the car, use our compass cards on Skytrain and/or bus. The Skytrain WAS going to have a station about 2 blocks from us, but the NIMBY forces relegated the nearest one BEYOND the far-flung frInge of town; bit of a hike: cross a highway, under an overpass, and across acres of asphalt parking lots.
     
    #14 Mendel Leisk, Aug 19, 2021
    Last edited: Aug 19, 2021
  15. AzWxGuy

    AzWxGuy Weather Guy

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    If the OP ever comes back, I had a 2008 with a similar symptom. I had been watching the 5 year old 12V battery for signs of weakness for a while already. Another symptom is excessive engine idling as it attempts to charge the 12V battery that isn't holding a charge very well. That is what is knocking your mpg down. Pull the 12V battery and have it stress tested and you'll likely find it needs replacing.
     
  16. asjoseph

    asjoseph Samuel, '04 Ruthiemobile

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    ... want good fuel consumption? Change your way of thinking (e.g., coast; stop riding your brakes; turn off the a/c). Driving it like a Corvette? 37 mpg sounds about right.
     
  17. Another

    Another Active Member

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    After past due change of spark plugs, especially with 225k miles close to the 240k second milestone and no knowledge of the plugs were ever changed and if they were with what, I agree this is most likely the reason. No information on whether OP knows how to drive a hybrid. Learning curve is not that steep but a few points need to be observed.
     
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