Bad fuel economy: Pirelli P4 4 Seasons Plus

Discussion in 'Gen 2 Prius Fuel Economy' started by violinguy, Dec 22, 2015.

  1. violinguy

    violinguy Junior Member

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    My wife and I own two 2005 Priuses. We recently put a set of new tires on her car: Pirelli P4 4-Season Plus which were rated well for rolling resistance plus an 85K mile tread. Very soon after, my wife told me she was getting worse mileage. She has a relatively heavy foot, so she never got more than 43-46 mpg depending on season, but now she was getting 36-38! At the time I just thought it was the colder weather. Then I drove the car myself. I normally get upper forties mpg. I couldn't get it over 41 mpg. Engine sounded fine, No check engine light, recent oil change, recently changed PCV valve and relatively new spark plugs. I touched the rotors to see if they were getting hot thinking that maybe the brakes were sticking, and they were normal. So I suspected the tires as the culprit. I had them pumped to 42 / 40 so it wasn't an issue of underinflation. I decided to do the crazy thing and to take all 4 of my tires off my car and switch them to her car. As a side note, I forgot to set the emergency brake and one car was on a slight slope and it rolled off the jack! That made for a more exciting afternoon ! After a test drive of about 30 miles it proved the case that the Pirellis were creating much more drag. The tires that were now on the vehicle were Bridgestone Ecopia. I was hitting upper forties again. Soon I will be taking my car out for a drive to see if indeed my mileage has dropped from having the Pirellis on now. But I'm pretty convinced, that these tires do not do what they say they're supposed to do which is have low rolling resistance. I am also surprised that even if they don't have low rolling resistance, that it makes that much of a difference! Just FYI, the tires in question had about five thousand miles on them. Any ideas would be helpful, but if you are the typical Prius driver looking for the best gas mileage I don't recommend these tires!
     
  2. violinguy

    violinguy Junior Member

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    Just to add from tirerack.com:
    "The P4 Four Seasons Plus is Pirelli's Standard Touring All-Season tire developed for drivers of coupes, sedans and minivans. Designed to help reduce environmental impact, P4 Four Seasons Plus tires combine ride comfort, low noise and reduced rolling resistance with long life and four-season traction on dry, wet and wintry roads, even in light snow.

    Pirelli P4 Four Seasons Plus tires feature a silica-rich tread compound made possible through use of innovative materials and processing methods to reduce rolling resistance while enhancing foul-weather traction."
     
  3. uart

    uart Senior Member

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    Yeah, the problem with manufacturer claims like "low rolling resistance" or "reduced rolling resistance" is that with current consumer law it seems that there's no obligation for them to quantify exactly what that means. Low compared to what? You see what I mean, it's pretty vague.

    It's kind of like advertising something as "light weight" without ever needing to state the actual weight. If you think it's a selling point to state that, then why not? It has to be light weight compared to something right, and you haven't made any specific claim of the actual weight that anyone can hold you to. So yeah, if you think it will help you sell the product then why not make the claim.

    Ultimately, for this reason, I think manufactures claims of low or lower rolling resistance are often a bit meaningless these days. I'm very dubious about it unless I've seen actual tests or positive fuel efficiency results from other users that I trust. Personally I think that if manufacturers claim LRR that they should also be obliged to state the actual CRR (coefficient of rolling resistance), but sadly none do so. :(
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Thanks for the heads up. Pretty pathetic when a tire purporting to be LLR is so bad.

    Hey, a good Boxing Day purchase: wheel chocks. :)
     
  5. uart

    uart Senior Member

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    Yep I agree. But we've seen this type of thing reported so often that I'm certain this is not just a "one off" with this particular tire. Unfortunately you just can't trust vague product descriptions like "super heavy duty" or "ultra high capacity" to carry much meaning when those things are not quantified in any way (in the product claims).

    I mean if I go out and buy some flashlight batteries that say "super heavy duty" on the package, there's no real guaranty that they will last any longer than some other brand's batteries that don't make that claim. Sure I might hope that they do, but I've lived long enough to know that without something quantifiable (like a mA-hr rating) that there is just no guaranty.

    Unfortunately this seems to be the way the term LRR is going in manufacturer's tire descriptions these days. They know it is something people are looking for, so as long as that particular tire has a lower rolling resistance than some other tire in their range then they can say it's low (or lower) rolling resistance. I really think there should be some definitive CRR level that they have to meet to claim LRR, but at the moment I don't think that's the case. Lot's of people have reported this type of thing here before, where the manufacturer's blurb for some tire has mentioned LRR but they just haven't lived up to expectations.
     
    #5 uart, Dec 25, 2015
    Last edited: Dec 25, 2015
    Mendel Leisk likes this.
  6. Black2006

    Black2006 Member

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    I just decided to try the Pirelli P4 Plus, to replace a set of five-year old Michelins which were disintegrating fast (tons of side cracks and one blew up a couple of days ago).

    So far, the ride on the Pirellis seems perhaps a bit softer and no noisier than with the Michelins, so I am happy.

    I live on a hill, so I was getting about 37 mpg with the Michelins, will see how it goes with the Pirellis and will post here.
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    What specific Michelin? Maybe contact them about the blow up.
     
  8. 09Prius2

    09Prius2 Member

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    Yeah, while it sounds like somewhat deceptive advertising as it kinda is, there are a few other factors in play.

    1. You purchased a tire with a better all season traction rating, so it is bound to have a meatier tread pattern in a addition to being heavier with more tread compound.

    2. The other tires were well worn, which increase mpg as the tire gets lighter and smoother, you gain mileage while losing traction. The new tire would certainly improve in mileage over time as it sheds weight and resistance.

    3. Driving with a lead foot drastically decreases mileage. Now that you have a tire that can do things the ecopia can't, you're bound to lose mileage in the spirit of utilizing your newfound traction.

    I'd say pump them up to the max and drive easy. It can't be a 20% difference from the tire alone, assuming its the exact same size.
     
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