Welcome to Our Community

Wanting to join the rest of our members? Feel free to sign up today.

Sign Up

Tips to revitalize a slowly-decreasing mpg 2006? (160K miles)

Discussion in 'Gen II Prius Fuel Economy' started by Soylent, Apr 9, 2012.

Social Buttons

  1. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three
    I have been driving this vehicle since late 2006 in South Florida, basically the same type of driving since day one (commute, family, store, etc.). The 160K is 95% highway miles, due to my 75 mile daily commute.

    Over the years, my average mpg has slowly decreased. Brand new, I could expect 46-47 average. Then it stayed at 45 average for a couple years. But after 4 years, it dropped to 43. Now, at 5 1/2 years old, I'm getting about 41 average.

    I follow the same routine-
    -Strict 5K oil changes and tire rotation (same dealer each time).
    -Mileage drops temporarily when I replace the tires, until they wear in.
    -Florida weather has been pretty much the same over the years (hot, humid), so I always run A/C.
    -Buy fuel at the same gas stations on my commute.

    I'm assuming that it's just wear/tear, and possibly an aging battery. But at 160K, is there anything else I could do to bring back those extra couple mpg's?

    Update: Link to post where I installed a new 12v battery
  2. ksstathead

    ksstathead Active Member

    Joined:
    May 1, 2007
    Messages:
    1,234
    Likes Received:
    226
    Location:
    Kansas
    Your Vehicle Year:
    2010 Prius
    Model:
    III
    Tire pressure variance? Type of tire variance? Dieing 12V? Dirty throttle body or MAF sensor? Alignment? Maybe traffic or your driving has gotten worse for mpg?

    These are a few of our favorite things. Use trip B and see if your steady state mpg in good conditions is in line with norms.
    1 person likes this.
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    Messages:
    7,576
    Likes Received:
    2,264
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three
    1 person likes this.
  4. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three
    Now that I think about it, I believe I still have the factory 12V battery.
  5. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    Messages:
    7,576
    Likes Received:
    2,264
    Location:
    Greenwood MS USA
    Your Vehicle Year:
    2012 Prius v wagon
    Model:
    Three
    It may not be the problem, but it is surely nearing end of life.
    1 person likes this.
  6. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three
    I just tested the battery using the built-in check on the screen. The result is 11.7v under load, so I'm going to get a new battery asap, and update on whether there is any difference.

    I'll also try cleaning the Mass Airflow sensor as well.

    Thanks!

    Edit: Wow, that battery is almost $200...

    Attached Files:

  7. Genoz World

    Genoz World ZEN-style living

    Joined:
    Feb 21, 2008
    Messages:
    797
    Likes Received:
    17
    Location:
    La Canada
    Your Vehicle Year:
    Other Hybrid
    Model:
    N/A
    Also, make sure you clean the sensors, change the air filter and use 42/40 in the tires.
    1 person likes this.
  8. ksstathead

    ksstathead Active Member

    Joined:
    May 1, 2007
    Messages:
    1,234
    Likes Received:
    226
    Location:
    Kansas
    Your Vehicle Year:
    2010 Prius
    Model:
    III
    Optima Yellow Top may be a bit higher still, but probably handles the job better.
    1 person likes this.
  9. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    Messages:
    3,602
    Likes Received:
    755
    Location:
    Australia
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A


    It would be really interesting if you change just the battery first off, and let us know if there's any improvement. The situation with the 12V battery change is that some people notice a marked improvement in MPG but on the other hand many people see no effect at all.

    If the 12 battery change has no effect then not to worry, yours would probably have crapped out soon anyway. In this case move on to getting the MAF sensor cleaned and also consider adding a bottle of a good fuel injector cleaner to a tank of fuel.

    BTW. What tires (exact brand model size) are you currently running, and roughly how many miles do you have on them.
    1 person likes this.
  10. Sabby

    Sabby Member

    Joined:
    Sep 17, 2011
    Messages:
    229
    Likes Received:
    77
    Location:
    NY
    Your Vehicle Year:
    2011 Prius
    Model:
    Two
    Next time the car is on a lift make sure you do not have any brake dragging either with the calipers, drums or emergency brake.
    1 person likes this.
  11. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    Messages:
    3,326
    Likes Received:
    1,437
    Location:
    Santa Fe, NM
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    It could even be that your A/C charge is low so the compressor is working harder, which drains the HV battery and causes low mpg. It would be a good idea to have it checked at some point, but it is a ways down the list of possibilities.
    1 person likes this.
  12. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three


    I had the AC serviced recently. It blows very cold, but I have noticed that it doesn't blow very hard. Sometimes when it's in the 80's outside, the blower seems like it's on low. I have to set the temperature to 70 or lower before the blower kicks up to maximum.
  13. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three


    Yokohama AS530. So far the best tires I've used, and I always had Michelin Hydroedge before.
    I think I have around 15-20K miles on them.
  14. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    Messages:
    3,602
    Likes Received:
    755
    Location:
    Australia
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A


    I don't think that's a low rolling resistance tire, so that could be at least part of your problem.

    Also, what size are your tires, stock 185/65/15 or otherwise?
    1 person likes this.
  15. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three


    Stock size. I don't think I ever had special low resistance tires. Before the Yokohama, I always used Michelin Hydroedge.

    The AS530s are also rain tires, so I'm not sure they would make such a difference in resistance.
  16. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    Messages:
    3,602
    Likes Received:
    755
    Location:
    Australia
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A


    Ok, so that's stock size for non-touring model, 185/65/15, good.



    I don't think the hydroedges are too bad, though they're definitely a little higher rolling resistance than the OEM's. There's also "hydroedge with green X" which is fairly low rolling resistance (though still nowhere near the current best LRR performers).

    The AS530s I really no nothing about, other than no one is listing them as LRR tires or making any specific LRR claims about them.

    I'm not saying that tires are your only issue. I just want to point out that tire choice is extremely important to fuel efficiency. A poor choice of tires can easily drop your MPG's by 10%. So at least part of your problem may be that you've gone for successively worse performing (in terms of LRR) tires over time.
    1 person likes this.
  17. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three


    That's a good point. I find the AS530s to have superior grip compared to the Hydroedge, especially on wet pavement. The Michelins were also seemed more fragile, and felt and sounded like riding on overinflated basketballs.
    So its probably the AS530s are heavier or bulkier.

    Still, like you said, it would only be a contribution to the problem. I started seeing mpg drop while still on the Michelins.
  18. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three
    Ok, here's an update. Just got back from Toyota and finished installing the new battery. First of all, I have to say that is the most difficult time I've ever had replacing a car battery. Seriously, they made that thing really hard to get out. I think it took me about an hour.

    I drove it around for a few miles. Not enough yet to measure any change in mpg (which I will monitor over the week), but I did immediately notice a few improvements.

    First of all, the A/C blower now runs much stronger. I actually started getting too cold, because I was used to setting the temp to 70 just to get it to run. Now I had it at 75 and it was freezing.

    The engine kicks in more smoothly and quicker. I realize now that the engine still have to "turn over", except at a higher RPM. With the battery being near-dead, it clearly wasn't turning over efficiently.

    And also a light bulb came on (in my head). One of the things that had baffled me for years was a weird, whiny sound coming from the engine at random times. In fact here is the link to the forum post, http://priuschat.com/forums/gen-ii-...73-noise-coming-front-car-audio-included.html. It sounded like it was coming from the coolant pump (the thermos reservoir thing), but I could never verify it and everything seemed to be running fine anyway. So I just left it, and eventually it went away.

    Today, after I shut off the car, I heard something I haven't heard in a long time, (and never noticed it had stopped); the coolant pump kicked in.

    That pump was not running for the last 2 years.

    So that probably answers my post from 2 years ago. The battery voltage was too low for the pump to start, causing it to make that "dying" sound. Then it stopped completely. But now I have more questions... why didn't any warning lights come on? Why didn't the battery every get checked in 2 years of service?

    Most perplexing is why didn't the battery just die outright? How could it still be starting the car?

    Anyway, you guys are awesome. A round of thanks to everyone who helped. I don't know if the mpg has been affected, but I feel like the car works so much better now. And it only cost me $200 and an hour of work. :)
  19. kocho

    kocho Member

    Joined:
    Oct 16, 2007
    Messages:
    135
    Likes Received:
    2
    Location:
    Maryland
    Your Vehicle Year:
    2008 Prius
    Model:
    N/A
    A bit of placebo effect, perhaps? I'm not sure why the 12v battery would have any effect on the engine "turning" - as far as I know power for that is supplied by the big hybrid battery, not the small 12v one you replaced.

    I am not sure if that is the case for the A/C - is that electric in the Gen 2 and if so, does it run on 12v or the hybrid battery? How about the coolant pump? I don't know, so I'm asking...

    I can imagine a bad 12v battery will decrease fuel economy since it would have to be charged more from the hybrid battery so more losses down the drain. Other than that, not sure anything should be impacted by a weak 12v battery really - once the car is running, power comes from the charging system like on a regular car, except it goes via the hybrid battery first in the Prius...

    I should add that I'm interested in this 12v thing since my newly acquired '08 probably still has its original battery and when I measured via the screen last night it was 11.7v or so at no load , and a tenth or two less at load. 14v with charging...Fuel economy is OK though - when I drive it would be 50 in city traffic on the MFD, 47 for my wife, even though I got upsized non LLR tires (195-60/15 Michellin Primacy MXV4 at "only" 36 psi front, 34psi rear)...



  20. Soylent

    Soylent It's not a station wagon! It's just big boned

    Joined:
    May 2, 2006
    Messages:
    426
    Likes Received:
    6
    Location:
    Fort Lauderdale, Florida
    Your Vehicle Year:
    2013 Prius v wagon
    Model:
    Three


    You may be right. I was under the impression the ICE was started by the 12V battery. If it dies, you can't start the car.

    As for the AC, some components must be run by the 12V. The blower runs when the car is on but in ACC mode. The condenser doesn't operate in ACC mode though.
Similar Threads: Tips revitalize
Forum Title Date
Newbie Forum New Prius Three Today - Need General Tips Jul 14, 2014
Prius v Main Forum Maintance Tips - fluids, etc. Jul 2, 2014
Gen II Prius Accessories & Modifications HELP! any tips on installing a wheelskin that might make it a smoother installation? Jun 25, 2014
Gen III 2010+ Prius Fuel Economy What is your number of "miles to refill" upon fill up? Tips for calculating actual MPG? Jun 3, 2014
Gen II Prius Main Forum Tips for HV battery care? Apr 13, 2014