Very Low MPG New 2015 EX?
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Thread: Very Low MPG New 2015 EX?

  1. #1
    Greenhorn
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    Very Low MPG New 2015 EX?

    Hello All, I just got a brand new 2015 civic EX with 7 miles on the odometer last month. I've since driven about 500 miles in the car and have been getting much lower than the advertised fuel economy. Most of my driving has been in the city with some traffic (occasionally highway), and I've only averaged about 23.5 MPG (based on manual calculation; iMid has similar numbers). I was wondering if this is normal to get such a low number, or if I should get the car checked at the dealer. I've been running the car with the ECON button on, driving extremely smooth, coasting where possible, accelerating smoothly, with the A/C off. I've checked Fuelly and this kind of number seems to pretty much be non-existent with most people getting at least 27MPG! I am in California if that matters, driving around the Los Angeles area. Thanks!

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  3. #2
    Nooblets ROWWWEL_808's Avatar
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    The motor is still breaking in so you're not gonna get good MPG right off the bat. As the motor breaks in though you should be seeing much better numbers. Maybe after a couple thousand miles.
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    Truck? What truck?! scottyrocks's Avatar
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    Welcome to 9th gen.

    Let it go through its break-in mileage. You should see some improvement after that. My '12 LX got 24 to 25 mpg in heavy-congestion traffic all its life, but could do 40+ on the open road.
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  6. #4
    Platinum Member SICoupe's Avatar
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    ^ agree with above posts
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  7. #5
    One Bad Mama Jama!!! bigbadspoon's Avatar
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    City fuel economy is a heavily variable number. I haven't been to LA in like 10 years, but last time I went, I spent 80% of my time idling on the freeway. If it's still like that, 24 mpg seems pretty reasonable. If you want to see your MPG take a huge jump, shut off the engine when your car is going to be sitting for more than 30 seconds.

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    Thanks for the replies guys! I'm hoping it goes up soon if that's the case with the break-in period. I was just surprised that I wasn't able to find anyone else with such low MPG, considering how many civic owners there would be in the LA area and other congested metropolitan regions (if they get similar fuel economy). Most of my time driving consists of some stops signs and stop and go on traffic lights on 30-40mph roads, but not any heavy traffic as I try to avoid that - that's why I was surprised by the low number. The most I've gotten was about 31mpg driving down the freeway for a bit, but I was just surprised that the city MPG was nowhere near the advertised 30MPG.

  9. #7
    Big Pimping!!! qingcong's Avatar
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    In addition to traffic and engine break-in as has been mentioned, other factors I can think of that might reduce MPGs -

    short trips
    cheap gas
    too much braking (seems you are aware of this)
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  10. #8
    One Bad Mama Jama!!! bigbadspoon's Avatar
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    Quote Originally Posted by alxz310 View Post
    Thanks for the replies guys! I'm hoping it goes up soon if that's the case with the break-in period. I was just surprised that I wasn't able to find anyone else with such low MPG, considering how many civic owners there would be in the LA area and other congested metropolitan regions (if they get similar fuel economy). Most of my time driving consists of some stops signs and stop and go on traffic lights on 30-40mph roads, but not any heavy traffic as I try to avoid that - that's why I was surprised by the low number. The most I've gotten was about 31mpg driving down the freeway for a bit, but I was just surprised that the city MPG was nowhere near the advertised 30MPG.
    Keep in mind that advertised MPG is based on the standardized EPA drive cycle. There are a lot of things it takes into account and a lot of things it misses. One of the things it appears to miss is traffic lights, as most of the stops in the dyno test are only a few seconds. It also only goes up to about 25 mph. Taking that same drive cycle and accelerating to 40 mph instead of 25 would use exponentially more fuel (E=0.5mv^2), even ignoring aerodynamics.

    Here's a link to the EPA drive-cycle that's used to determine the city mpg number.
    http://www.epa.gov/nvfel/methods/uddsdds.gif

    Also consider that using Fuelly as a source for mpg info may be a little skewed. Most of the people using that site are people who are consciously aware of their mpg and interested in fuel consumption. These tend to be more efficient drivers, in general. Especially given that Fuelly only has data for like 850 9th gen Civics. Since more than a million have been sold, I don't think 850 can be called a statistically significant sampling (I played with a calculator a little bit and came up with Fuelly being accurate to within ~3 mpg of the entire population of 2012-2015 Civics...not very good).

    There are a lot of hypermiling tips out there for people living in congested areas. It sounds like you understand the basics of hypermiling, but getting over 30 mpg in an urban area requires a pretty special set of skills and immeasurable discipline. My recommendation is to learn your light schedule and drive only as fast as you need to to get to the next light while it's green. Sometimes this means going 25 in a 40, but you'll probably never use your brakes . If you have to stop at a red light for more than 30 seconds or so, kill the engine. If your car has a manual transmission, kill it while you're coasting down (never *ever* do this in an automatic).
    scottyrocks and alxz310 like this.

  11. #9
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    Thanks a lot for the tips and explanation of the EPA test! The lights here sometimes take a long time to cycle and there's a lot of stop and go, with many traffic lights in a row; I'm beginning to think that has just been completely throwing off my fuel economy. I was also wondering, how long does a trip need to be for the engine to be properly warmed up / fuel economy to be the best?

    I managed to hit ~29mpg for the first time today driving on surface streets; I took a different route than usual and coasted around 40mph most of the time with a couple of traffic lights in between. This was also after driving around a lot earlier in the day. Going back with a mix of 70% freeway / 30% streets, I was able to get up to 31mpg... So it seems like driving in the LA area just makes it really difficult to get the estimated fuel economy without streets being unusually empty

  12. #10
    One Bad Mama Jama!!! bigbadspoon's Avatar
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    Yeah, LA is a beast of a city to get any good mileage in. I think those traffic lights are why hybrids are so popular there. Hybrids (non-IMA, at least), get their best mileage driving around the city, since the electric motor handles most of the acceleration.

    Anyway, as for how long it takes the engine to warm up...I pulled up one of my datalogs from a warm-ish day (66) where I recorded from startup and it took 3 minutes (1 stop sign, driving 35 mph) to get up to 143 degrees which, according to FlashPro, is the point where the ECU no longer compensates for the engine being cold. Efficiency only goes up as things warm up, though. When the engine gets warm, it heats up your intake tube a little bit (not a lot), but the warmer your intake temp is, the higher your volumetric efficiency becomes. In FlashPro, the software sweet spot looks to be 86 degrees of IAT, which is the point just before the ECU starts to pull spark. The actual sweet spot is probably higher, but I haven't done any testing to confirm. I ran a warm air intake on my old Civic and IATs over 160 degrees netted me about 4 mpg over the stock intake, this is because retarding the ignition doesn't necessarily have a negative impact on overall efficiency, as it should only retard just enough to prevent pre-ignition, but there's not an easy formula that defines this.

    I kind of got off on a tangent. Moral of the story is that the engine warms up in about 3 minutes. Trips less than that will have crappy economy, but anything longer than that should be pretty optimal from a temperature standpoint. Beating the EPA estimate is really just going to come down to practice. It sounds like you're already starting to get the hang of what techniques you need to bump it up as 31 mpg is a 29% improvement over your original 24.
    scottyrocks likes this.

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