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  1. #1
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    Sep 2008
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    2006 HCH Undeterminable Cause of MPG Drop

    I bought my 2006 HCH in 9/06. I use it mostly for back to work and occasional long trips. My driving is probably 80% highway at 55 or 65 mph. Up until about 6 weeks ago I averaged about 44MPG. Not bad considering the stop and go at high speeds on I95. About 6 weeks ago my mileage started dropping. For 2 or 3 tankfulls I was getting about 41MPG. The tires were then replaced with Bridgestone Potenza'ss. The next couple of tanks of gas the mileage was down to about 39. I thought that wasn't too bad for the different tires and the car does ride smoother.

    But the mileage kept dropping until it hit about 33 MPG which is where is has been for about a month.
    I've had the car to two different dealers to have it checked out. The first one said the transmission needed to be serviced and a part replaced (apparently a known problem with the 2006 CVT transmission) and they serviced it under the warranty. No improvement in mileage. I talked to the service advisor and he told me its probably mostly due to the tires and the 10% ethanol that is being added to gas now. I went to another honda dealer and had them check the car over. They claim that everything is up to spec and it must be the tires. I can't believe that tires alone could cause that much of a drop.

    Before this had started I ran over a piece of metal on the highway. I had the car checked underneath and was told nothing was damaged. I'm wondering if something was bent so my next step is to have the alignment checked.

    Any suggestions on what else I should have checked/done? I replaced the air filter about a month ago, the oil is changed at the dealer and they tell me they use the recommended oil.

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  3. #2
    Junior Member
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    Oct 2006
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    Improper tire replacements

    Improper tire replacements are almost always the reason behind significant losses in fuel economy, and yet not many dealers know/care about this nor do many owners believe the choice of tires can have such an impact.

    The original tires were rated as LRR (low rolling resistance) and quite often they get replaced by brands and models that are nowhere near the same specifications and act little boat anchors in fuel efficient hybrids.

    Now, if you are stuck with the Bridgestone Potenzas I would suggest you do the following in hopes of mitigating the LRR loss:
    1- check the max pressure embossed in the sidewall of your new tires.
    2- inflate the front tires to 2 psi lower than the max pressure
    3- inflate the rear tires to 4 psi lower than the max pressure

    An alignment is always a good thing to do every so often. I do one every 2 years and it always well worth the expense when done properly.

    Oil changes are also critical especially when using anything but 0W20. Sometimes dealers will put in 5W20 and that will kill your fuel economy just as well. If a dealer has done this to your car, please take them to task and force them to put in the correct oil weight as recommended by Honda.

    Give the tire pressure advice a shot and let us know how it goes.

    Cheers;

    MSantos

  4. #3

    I've got the same year, and

    I've got the same year, and mileage averages around the same as your 41 mpg. This last summer we're usually around 5.5 liters per 100 km (or lower), doing a mix of around town and highway. Which translates to 43 mpg (US gallon).

    BTW, to convert btwn the 2 systems, divide either number into 236.5

    Per MSantos: your tires (and their pressure) are one very likely culprit, as is the oil type.

    One further thing, not sure if it's just my superstition: choice of gas stations.

    Also, good mileage seems to go by-by for us every winter.

  5. #4
    Junior Member
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    Sep 2008
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    I have no doubt that the

    I have no doubt that the tires contribute to the lower mileage. But if that were the major problem wouldn't I have noticed a large decrease right away? The MPG was gradually dropping over the preiod of about a month before it levelled off where it is now. And it had started to lower before I replaced the tires. I can't help but think that something was going wrong and finally failed after about a month.

    I have been watching the assist and regen very carefully. It seems like most mornings there is very little battery charge and very little assist during my commute.

    As far as gas stations, I have used several different ones.

  6. #5
    Junior Member
    Join Date
    Oct 2006
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    Hi EdBickford: The issues I

    Hi EdBickford:

    The issues I discussed above are the most typical cause in claims such as yours. FYI, new tires will exhibit varying coefficients of friction as they wear, so... I would not discount this issue for this very reason. We've seen hundreds of claims similar to your and they all share the same root problem. Sorry. Despite this, please inflate your tires as we recommended. At those pressures they are safer and they will wear better (contrary to the outdated belief in the minds on many in the tire business - a clear sign of lacking technical education).


    The only other thing that can explain a noticeable drop in FE is a failing high powered component that exhibits above normal power leaks. For instance, the electric power steering and the Climate control system are two of several worth looking into.

    Cheers;

    MSantos

  7. #6
    Guest

    I appreciate all of your

    I appreciate all of your comments and advice. I just want to make sure it can't be something else before I replace the tires again. As I mentioned I had run over a piece of metal before my mileage started to decline. It was a few weeks later when the right front tire blew out. I think what I ran over hit the tire on the inside as that is where the tire blew. Is there anything in that area that could have been hit that would cause this problem?

  8. #7

    One other thing I can think

    One other thing I can think of is some kind of brake drag. I find whenever we have our car in for service they cinch the parking brake way too tight. According to Shop Manual spec. if you jack up the back the wheels should turn freely (or nearly freely, maybe just a slight whisper at some point in the revolution), have *slight* drag with the parking brake pulled up one click, and be fully locked by 8~10 clicks. You can do a quick check by just testing on an inclined driveway.

    This is with the 06 hybrid. The adjusting bolt for the parking break is inside the center console. It's accessable but it takes a little finess getting the plastic panels off, and you need a long extension socket.

    Another thing is outside temperature. As I mentioned before, our mileage always goes to pot in winter. The car's computer is aware of ambient temperature, and adjusts settings based on it. If you do a lot of short trips, the longer warmups it does in fall/winter/spring are a factor

  9. #8
    Guest

    Welcome to my world. It

    Welcome to my world. It isn't the tires. The problem is that the IMA loses charge when the car is parked. As a result, in the morning, or after work, the battery has discharged and you spend the first 5-10 miles with no "assist" until the battery charges up again. I have submitted a formal complaint to Honda, but they are unwilling to accept fault. I will use your report as further evidence.

  10. #9

    Tires do cause a major

    Tires do cause a major mileage problem.But it is not a major problem.I don't think this will be the sole reason for your problem.

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