12V battery and Reduced MPG after new tires

Discussion in 'Gen 3 Prius Main Forum' started by kobear18, Dec 9, 2019.

  1. kobear18

    kobear18 Junior Member

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    Hi Every1
    I like to share some of my 2010 3rd gen prius. I bought it used with 82000 miles on back in Jan 2014. I changed the 12V battery on the 2nd day I got it. Now I got 236,000 miles on it. I drive it everyday and its got no problem starting. I got the 12V battery from Toyota dealer shop for $168. It was kinda expensive back then but maybe better quality so it lasts until now. I changed all 4 tires in August at costco. The new ones are bridgestone TURANZA QUIETTRACK. It should be good tires but it reduce the MPG a whole lot. Now im getting 43 to 44. When I first got it, it was at 46 to 47. I wonder why ? I used to have the Good year Assurance and it was always at 50. So I suspect that its the tires problem? I also did some stupid thing when I changed oil last time, I mix a lil bit of 5-20W with the 0-20W because I got a lil of 5-20W left. Maybe that made the oil a lil thicker and it reduced the MPG? I'm thinking of pouring some seafoam in it to make it thinner. Or is it the 12V battery getting oil and reducing the MPG? I still think its the tires problem. I want to get the Michelin energy saver but costco don't have them in stock. Im down for the goodyear assurance again.

    I'm also considering cheap tires like those $50 a piece ones. My theory is that the harder the tires, the more MPG because harder material tires rolls better. You may think it wears out faster. Yes it does but its still better to changed cheap tires every 1.5 to 2 years than having a $460 bridgestone quiettrack last 4 years but only do 44 mpg. Do you know of any harder material tires for cheap? Its prius, we usually don't drive too fast so the traction and wear out fast issue don't matter. All I want is 55+ MPG.

     
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  2. bisco

    bisco cookie crumbler

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    well,

    you've got 236,000 miles

    how many miles on the new tires? they might need a breake in. are they LRR?

    load test the 12v, no way to know otherwise. it's 6 years old, so maybe just replace it

    never heard of anyone praising hard tires. try pumping them up to the sidewall max pressure

    there are an awful lot of other things on a prius that can cause mpg problems as well
     
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  3. kobear18

    kobear18 Junior Member

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    For this new bridgestone quiettrack, I got them since August this year so about 6k miles on it
     
  4. bisco

    bisco cookie crumbler

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    that should be enough for break in
     
  5. Fifen

    Fifen Junior Member

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    New tires get better grip and that might be hurting your mpg. I normally get 50mpg. I got brand new Bridgestone Blizzak ws90 snow tires and now I'm barely getting 40mpg. Also cold temps and slick roads hurt your mpg

    SM-G965U ?
     
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  6. Grit

    Grit Senior Member

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    I just bought new tires 2 days ago, for 6 months I contemplated which tire replacement to buy when when my tires wears to 2/32". I had michelin defenders Green-X treadwear 820, those were discontinued so I was SOL because for the last 12 months my average MPG was 63-64 mpg. I looked at many many tires, even the new Green-X treadwear 480 but I decided to go with Michelin defender T + H because on paper, the T + H 820 specs were similar to the Green-X 820. I will not settle for treadwear rating lower than 800 if you haven't catched my drift heh. After 200 miles on the new tires, I kid you not I'm still getting the exact same MPGs. Below was the summary of test run the day after I got the replacements 50/50 highway & city driving; 71 mpg

    IMG_2592.JPG
     
    #6 Grit, Dec 9, 2019
    Last edited: Dec 9, 2019
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  7. Fifen

    Fifen Junior Member

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    There must be no hills where you live. On my best days I can only get 54 maaaaybe 56 if I drive boringly

    SM-G965U ?
     
  8. Grit

    Grit Senior Member

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    Correct, no hills. My commutes are country side and no one ever drives in front or behind me so no draft to even cheat for FE. But then again I drive w/o wipers installed and everything in back been gutted out to max out FE.
     
  9. Fifen

    Fifen Junior Member

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    There must be wipers on the front tho. Like what else would you do if it rains?

    SM-G965U ?
     
  10. bettergolf

    bettergolf Member

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    So it looks like you averaged somewhere near 30mph for almost an hour to get that 71mpg?
     
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  11. Grit

    Grit Senior Member

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    Read last sentence on post #6
     
  12. fuzzy1

    fuzzy1 Senior Member

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    While that sounds intuitively reasonable on the tread, I can't take it as a given, especially for the sidewall. Even a hard tire is still going to flex at and near the contact patch, including the sidewall. If material hysteresis causes those flexed portions to resist rebounding back to normal shape, rolling resistance will rise and sap MPG.
    Traction isn't needed to go fast. It is needed to stop quick in sudden emergencies, which happen at all speeds.

    So 55 MPG is the goal.. Have you looked at this?
    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

    How fast do you drive on the highway, or where-ever else is your fastest speed? If it is above 65, fuggedaboutit, even for a pristine new 2010 Prius:
    Updated MPG vs MPH chart
     
  13. bettergolf

    bettergolf Member

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    I saw that, and the numbers average to near 30mph...I think I could get that averaging 30.....maybe? I'm going to try it and find out, lol....
     
  14. Grit

    Grit Senior Member

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    You'll get similar results, no doubt. But my test was half and half so it's real practical driving. You should see the top 10 list of farthest miles driven by the tank of gen 3s. 1st place average speed was 20 mph! I'd kill myself if I was the passenger in that car, going that slow for long trips. Sand pounder as a PC member would say.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    Do note that the average speed is not a moving average speed. It counts all the on-but-stopped time too, while parked, at stop signs, stop lights, stop-and-go traffic, waiting for traffic to clear before turning or pulling out, etc. So it likely includes some time at significantly higher speed.

    At a steady speed of 30 mph, from a warm start, this car can exceed 90 MPG displayed. See that MPG vs MPG graph linked at post #6.
     
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  16. bettergolf

    bettergolf Member

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    Where can anyone drive 20mph for a full tank of gas without getting a ticket for going too slow, or rear ended by an irate driver stuck behind him?
    Reminds me of a long ago story where I had to stay under 30 for 5 hours on a busy 2 lavn highway because of 3 broken lug studs....don't even ask, I was about 20 at the time. Never saw so many birds flying by in my life! HA!
     
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  17. 2012 Prius v wagon 3

    2012 Prius v wagon 3 Junior Member

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    No problem at all.
    No sunroof, so stick head out the window. Squinting and blinking to see through the rain. Cruise control in case gas pedal can no longer be reached. But really, when you're doing 35 mph, you're mostly looking out the back window at the angry drivers behind you.
     
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  18. fuzzy1

    fuzzy1 Senior Member

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    There are places to do that, even in the U.S. Don't think in terms of busy Interstate highways.

    The serious full tank records come from Japanese commuters, apparently on routes where low speeds are natural.
     
  19. bettergolf

    bettergolf Member

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    I stay off the interstate every chance I get. I live in central NC and going to the mountains or the coast, I'd rather take an extra 45 min to get there and see the sights and small towns. I live out in the forest and even around here people try to push you if you stay at the speed limit.....every one's either late or just in a hurry!
     
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  20. kobear18

    kobear18 Junior Member

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    yes I live in San Francisco so there are a lot of hills. That take some MPG off I know.
    Scotty Kilmer said that 12V starter battery can also affect the MPG. Mine is 6 years old but I don't feel any problem though. It starts just by 1 push but he said the voltage maybe low although it still works to start. I'm also thinking that the hybrid battery is almost to the limit. Its 236300 miles now. I heard that the hybrid battery start going bad from 280000 to 330000 miles. So it starts to get lower MPG a lil by lil?
     
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