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04-07-2013, 05:08 PM | #176 |
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My 2012 is not a PZEV. I pre-ordered it and it was one of the early builds. I swapped out the OEM tires and pay a 1 or 2 MPG penalty, something that I am willing to do for the decreased noise and improved traction.
Something to be said about "Stats, Damned Stats, and Lies" though. Statistically, I get between 6 to 8 MPG better gas mileage than my son. He gets in the neighborhood of 24 or 25 MPG in urban driving. Now, how does that skew the "deltas"? He is also about 100 lbs heavier than I am - maybe that, along with his heavy right foot has something to do with the MPG.
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04-07-2013, 08:14 PM | #177 | |
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04-07-2013, 09:14 PM | #178 |
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That's what I thought. Statistically, that wouldn't matter - even though in the "real world" it could. But then what do I know, I'm not a math major - just a computer programmer (crap in equates to crap out in all cases)...
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04-08-2013, 03:42 AM | #179 | |
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So basically what we are saying is that the two different tests come within about one mpg of each other most of the time. Except when you throw in the Subarus. Then the Impreza CVT comes back six mpg low on a real road compared to its EPA highway estimate. But hey, if you think that's normal... |
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04-08-2013, 08:07 AM | #180 |
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Yes, normal.
http://autos.yahoo.com/news/here-s-w...175746134.html Either slow down or sell the car, but everyone is tired of your bitching about it, especially when you routinely speed and have a very large hill to climb daily. |
04-08-2013, 08:55 AM | #181 | |
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The article you linked to is about individual drivers and their correlation with the EPA test numbers. This is about systematic error. There are two types of error. Random Error and Bias Error, aka Systematic Error. I am talking here about how closely Consumer Reports' tests correlate with EPA tests. They won't be perfect either, especially considering the different methods. The differing methods means there likely will be a bias offset (aka systematic error) in the results, and indeed there is. However, in this case when that systematic error is removed, the two tests are usually within one mpg of each other in this case (unless Subaru is involved that is). However the Subaru Impreza CVT is 6 mpg away from the others, advertising said Impreza CVT as 6 mpg better than in reality. Reality as in the real world. That is not a random error, that is a systematic error in the measurement of the Impreza CVT mpg. That error is so big that in terms of the bell curve (which I guess you have not heard of) there is a one in three million chance it's normal. That is your position - that it's normal. Sorry, but it's not. That's okay, so you are not good in math. Except you are apparently not good in reading or logic either. This is about the Impreza CVT. You have a manual transmission. That is different. In fact according to Fuelly.com the manual gets better mpg than the CVT. The bottom line (what a coincidence, it actually is) is that if you are tired of looking at the posts in this thread, then don't look at this thread because THIS THREAD HAS NOTHING TO DO WITH YOU. Last edited by stevehnm; 04-08-2013 at 09:04 AM. |
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04-08-2013, 09:08 AM | #182 |
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04-08-2013, 09:26 AM | #183 | |
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since reading comprehension is difficult for you
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04-08-2013, 10:14 AM | #184 | |
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P.S. but your car does get a lot closer to the EPA estimate than the CVT, which you don't have and is what this thread is about. |
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04-08-2013, 10:47 AM | #185 | |
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If you drive your 5 speed at the same speeds, on the road he is driving it on, don't you know it would give you even better mpg's? lol |
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04-08-2013, 02:31 PM | #186 |
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#1 I have a 2012 CVT so maybe I'm qualified to post.
#2 I hate statistics. They can be manipulated to show whatever you want. #3 These numbers are from Consumer reports printed edittion that I have. first number is Consumer reports MPG. The last 3 numbers are city-average-highway for EPA. Subaru Impreza Prem _____27_____27-30-36 Mazda 3 Skyactive (auto) _____32_____28-33-40 Mazda 3 Grand Tour(2.0) _____25_____25-28-33 Ford Focus SFE (auto) _____31_____28-33-40 Chevy Cruze Eco _____27_____26-31-39 Chevy Cruze _____26_____26-30-38 Ford Focus SE(auto) _____28_____27-31-38 Honda Civic _____29_____28-32-39 Toyota Corolla(MT) _____32_____27-30-34 Jetta TDI _____34_____30-34-42 Dodge Dart _____27_____27-31-37 Jetta (2.5) _____25_____24-26-31 Yes the Subaru number is lower than some. But matches the City EPA number. Most others are within 1 or 2 of the City Number. Big deal?!?! I think not. Its very close to what most cars return for MPG. Last edited by jd_24; 04-08-2013 at 02:40 PM. |
04-08-2013, 02:39 PM | #187 |
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The Mazda 3 was still 8mpg less than its highway number, but better than its City number. The Corolla did well. The Jeta TDI Did well to, but still far from its highway numbers.
All the rest basically returned the CITY EPA during the Consumer Reports tests. |
04-08-2013, 02:45 PM | #188 |
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With the warmer temps (30s and 40s) here in Minneapolis my MPGs have risen. Most of the winter MPG was around 30 to 32 for my commute. Current tank is displaying 36.6mpg which will equate to about 34+ MPG with slightly over 1/2 a tank used.
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04-08-2013, 02:58 PM | #189 |
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Can't wait to see the results of the fuzzy math based off these numbers. Could you post the month and year of this consumer reports magazine. Looks like I should get a Honda civic
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04-08-2013, 03:02 PM | #190 | |
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We just signed up for Consumer Reports this past winter. 2013 auto issue. Why the Civic? Only +1 over the City EPA. Mazda 3 with Skyactive seems to return the best. However statistically its probably the Corolla. |
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04-08-2013, 04:18 PM | #191 | |
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i am actually quite surprised by the Honda Civic numbers being low. i haven't admittedly driven the new generation myself, but i know someone who bought one last year and i also looked at the fuelly numbers and they are significantly higher than the Impreza real world. but i agree with the point made here. if we want to do a somewhat reasonable statistics of the CR mileage numbers, we shouldn't just cherry pick cars getting 30mpg in the test. but rather, use the entire database available ranging from high to low mileage cars. the numbers in the above survey actually make a reasonable study, nevertheless, since it focuses on the small cars class which is presumably what a typical customer might be considering. |
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04-08-2013, 06:19 PM | #192 |
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I took all the cars that got 35 mpg highway in Consumer Reports. I didn't cherry pick the data.
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04-08-2013, 06:27 PM | #193 |
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04-08-2013, 06:39 PM | #194 | |
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this discrepancy speaks to the likelihood that there is no simple way to get sound statistics for this comparison. i was suggesting that for a more grounded approach, both you and JD could do the same analysis for all cars and see what kind of standard deviations you get. even then, i would be surprised if you got a different conclusion. (highway vs. city comparisons) i do agree that CR is a good starting point, for this tricky comparison, because at least the driver variable is nominally removed. (although i'm sure they have a whole staff of drivers they use for these tests) i should also note that I do get what you are saying. i can meet EPA numbers on the Impreza, but it requires far more effort than most of the previous vehicles i've driven/owned. if i were to rate the Impreza based on my prior cars EPA estimates, i would have thought that the Impreza were rated as 25/32, rather than 27/36 for the CVT. (although i should note that most of the cars i have driven were MT, so maybe that makes the personal comparison somewhat unfair, too) |
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04-08-2013, 11:07 PM | #195 |
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I went with highway mpg for two reasons. One was because it would be extremely repeatable - one the one hand we have the "hallowed" EPA test results, and on the other a two way constant speed run at 65 mph. The other reason, frankly, is because that is what I am concerned with.
Overall then, I don't do enough "city" or "combined" driving to worry about it, and making it repeatable with continuous repetitive acceleration and braking seemed difficult to replicate - and with the wide spread in results that seems to be the case. On the other hand, the highway mpg correlation was astonishing - usually within one mpg. Except the Impreza CVT... One in 3 million off the mark... |
04-08-2013, 11:41 PM | #196 |
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If you are using highway MPG and a constant run speed of 65 mph - that is NOT the way that the EPA measures it. Static skew? Data used for statistical analysis should be "pure" - I don't think your's is. Just MHO. Skew the data = skewed results.
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04-09-2013, 12:18 AM | #197 | ||
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Like most of the cars, the Impreza got right around it's City MPG figures, and only the TDI was able to hit the combined numbers. There must be a problem with the Impreza CVT because it performs like most of the other cars tested. |
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04-09-2013, 12:38 AM | #198 | |
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Now we have the two types of error - random and bias, established as a standard deviation of 1.19 mpg and an average of 6.3 mpg systematic, respectively. It becomes clear once one recognizes and separates the two types of error. So what we do, then is take your "skew" and remove it - it could be a constant offset or a percentage offset - it really doesn't matter in this case. Then we see that the two measurements - CR and EPA - usually differ by less than one mpg here (except for the Impreza CVT, of course, which is not just in left field, but in a different county so to speak). I don't think we can define the different errors as well with city or combined due to different throttle responses etc, verified by the increased range of the results. P.S. If you're still here... Standard Deviation is quite a cosmic thing, actually. It represents the Normal distribution, or Bell Curve. The bell starts from -infinity (it actually never goes to zero), then ramps up as it approaches the average - aka "concave up". Then when it gets close to the average it changes from concave up to concave down (inflects). Then it goes up to the average, then continues concave down to a point where it again inflects and becomes concave up and runs on out to +infinity. Anyway it is universal in nature and mathematics (mathematics is just a crystallization of nature when you get down to it). Those points where it "inflects" or changes from concave up to concave down or vice versa are at what are referred to as "one standard deviation" because between them are clumped most (about 65%) of the data. Even further if you have held on this long is that highway speed limits are set (or should be, to maximize safety) at the "85th percentile of the unrestricted speed" - the 85th percentile is right about one standard deviation above the average unrestricted speed, where most of the traffic is considered encapsulated in the average, and that above is kind of out in lala land where the data starts to just spread out. "Lala land". That's a technical term... Last edited by stevehnm; 04-09-2013 at 01:11 AM. |
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04-09-2013, 01:26 AM | #199 | |
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Cruze ECO gets same MPG as Impreza even though rated higher and plain Cruze gets lower MPG in spite of a higher rating. Looks like the Impreza performs comparably. I don't have a subscription to CR but I'd love to see the test data on the actual highway numbers for the above compacts and steves list of V6s and premium drinkers at 55, 65, and 75mph. That would be quite enlightening wouldn't it? Does that impartial data exist? My bet is that the CVT Impreza would whip the premium drinkers and V6s at 55, be a bit better at 65, and match them at 75. Any takers? |
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04-09-2013, 01:30 AM | #200 | |
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