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11-16-2012, 11:48 AM | #2351 | |
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Location: ND
Vehicle:2012 2.0i Sport 5MT DGM |
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11-17-2012, 06:43 AM | #2352 |
Scooby Newbie
Member#: 315883
Join Date: Apr 2012
Chapter/Region:
E. Canada
Vehicle:2012 IMPREZA Silver |
Latest fill up.
625.3km 100% city. 8.6l/100km actual. Avg temps 3c about to do first oil. Total mileage 6903.6km Pretty close to the suggested numbers and that's fine with me! When it was a little warmer I was getting about 8 so not too shabby. |
11-17-2012, 06:59 AM | #2353 |
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SCIC
Location: Los Angeles, CA
Vehicle:2012 Impreza WRX Ice Silver Metallic |
Tuned on 91 with a 3" cattless downpipe and intake I'm getting about 15/22
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11-17-2012, 09:13 AM | #2354 |
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Join Date: Jul 2012
Chapter/Region:
South East
Location: Florence SC
Vehicle:2017 Forester XT LPB |
Getting 27.3 and just over 2500 on the odometer miles almost pure city driving.
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11-17-2012, 12:14 PM | #2355 |
Scooby Newbie
Member#: 319378
Join Date: May 2012
Chapter/Region:
MWSOC
Location: West Central MN
Vehicle:2012 2.0i Sport Ltd. Satin White Pearl |
I lost about 3mpg with the switch to winter gas I think, like night and day. Other than that, I haven't noticed any change in average mpg after almost 10,000 miles.
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11-17-2012, 12:23 PM | #2356 |
Scooby Newbie
Member#: 316315
Join Date: Apr 2012
Chapter/Region:
MWSOC
Location: Mequon, WI
Vehicle:2012 Imp HB/Prem/CVT DCP |
My mileage immediately dropped 3-4 mpg on the last fillup 3 weeks ago. Temperature and weather was the same before and after. Funny thing was, it was only a 6 gallon fillup, so most of the gas in the tank was the older gas. All brand-name gas. Curious.
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11-17-2012, 12:56 PM | #2357 |
Scooby Specialist
Member#: 322264
Join Date: Jun 2012
Chapter/Region:
Tri-State
Location: Webster, NY
Vehicle:2012 Impreza Sp 5sp Obs Blk Prl/Drk Gray Mtl |
I just installed snow tires on my Impreza, and then immediately topped off my gas tank and zeroed my odometer so that I can see how much effect the snow tires have on MPGs.
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11-17-2012, 01:43 PM | #2358 |
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Join Date: Apr 2012
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Location: Atlanta Ga
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ok i really think it has more to do with the fact that the car is running rich for longer warming up than any winter fill vs summer fill.
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11-17-2012, 04:33 PM | #2359 | |
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E. Canada
Vehicle:2012 IMPREZA Silver |
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11-18-2012, 01:39 AM | #2360 | |
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Chapter/Region:
NESIC
Location: Massachusetts
Vehicle:2012 Impreza LTD Marine Blue Pearl |
Quote:
Maybe there is a physicist out there who could comment on this? |
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11-18-2012, 06:11 AM | #2361 |
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Join Date: Jun 2012
Chapter/Region:
Tri-State
Location: Webster, NY
Vehicle:2012 Impreza Sp 5sp Obs Blk Prl/Drk Gray Mtl |
^^ I don't think this is the valid explanation. I think it's simply that an engine (or furnace, or boiler, or kerosene heater, or oven, etc.) work most efficiently when they're hot. So the warm-up time is when our cars get crappy MPGs. Once they warm up, they're fairly efficient.
In the winter, it takes longer for the engine to warm up because the starting temp is lower, and because the air blowing into the engine is colder, so it takes longer for the engine to reach max efficiency. Add to that the winter blends of gas, and you take a double-whammy on your MPGs. |
11-18-2012, 09:22 AM | #2362 |
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Join Date: Aug 2012
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SWIC
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Vehicle:2013 Impreza Spt cvt Silver |
There are actually several factors why fuel economy suffers in the winter. The biggest, depending on your driving style, is that cold air is just more dense than warm air. That means several things are happening. For one, you are pushing more air - up to 10% more. Another reason is that as a certain volume of air comes into the engine, in the winter that has more mass so there is more fuel put in to compensate. Then, fluids are more viscous (thicker), which increases the power drag - things like transmissions and differentials that don't have cooling "systems" are more of a drag. Tires have less pressure so there is more rolling resistance.
The other reason, which may be major depending on your driving habits, is that people tend to warm their cars up more in the wintertime and take more shorter trips instead of walking or riding a bike, and it does take longer for all of the engine to warm up to optimum temperature in the winter (even though the gauge may say it's already warm). So, the answer is: It depends... |
11-18-2012, 09:56 AM | #2363 | |
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South East
Location: Atlanta Ga
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Quote:
Last edited by auskip07; 11-18-2012 at 10:16 AM. |
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11-18-2012, 11:13 AM | #2364 |
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Join Date: Oct 2004
Location: MD
Vehicle:2008 STI Boost Wagon 2014 Honda Accord Hybrid |
When the car is cold (and it is colder longer in the winter time) the engine is in open loop. While in open loop fuel is dumped into the engine at a higher rate than when in closed loop. This could add to the larger consumption during the colder months.
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11-18-2012, 11:18 AM | #2365 | |
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Chapter/Region:
MWSOC
Location: Mequon, WI
Vehicle:2012 Imp HB/Prem/CVT DCP |
Quote:
Mostly, in cold weather, you have the issues that others have pointed out: fluids are thicker and take much longer to warm up, so have more resistance and take more power to move engine parts in contact with the fluids. And then there's the winter gas issue: According to this, winter gas has more butane, which has less energy, resulting in up to 1.7% lower energy output. (Not a physicist). |
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11-18-2012, 11:34 AM | #2366 |
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Member#: 319157
Join Date: May 2012
Chapter/Region:
MAIC
Vehicle:2012 Impreza 4DR 5MT |
As long as the engine is running at operating temperature, it doesn't make much of a difference whether the excess heat is shed through the block or radiator.
The problem I'm seeing is that the engine sometimes struggles to maintain operating temperature, which definitely has an impact on efficiency. Most of the engine's power goes towards moving the air you drive through. In the winter, this air becomes more dense and provides more resistance. |
11-18-2012, 11:49 AM | #2367 | |
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Quote:
Moving the air (wind resistance) is in fact generally the largest factor in fuel consumption rate, once you're warmed to equilibrium. If it's 50% (and that will be determined by the aerodynamics of the vehicle) and density is increased by 10%, you can expect your fuel consumption to increase by 5%, all other things being equal. As far as colder air intake, the increased available power from the colder, more dense mixture going into the combustion chambers is offset, at steady state, by needing less weight on the accelerator pedal. It's the change in density, not temperature, that affects the available power. |
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11-18-2012, 12:13 PM | #2368 | ||
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Chapter/Region:
MAIC
Vehicle:2012 Impreza 4DR 5MT |
Quote:
If you have a scan tool, see for yourself. The blue light going out only indicates 120F. Quote:
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11-18-2012, 12:44 PM | #2369 |
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I have a Scangauge so will check that. I think you are probably correct in your generalization about "most cars" and 25 mph, but I'm not sure about the smaller much more aerodynamic cars like the Impreza. It might be 40 or so, due to the extra differential
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11-18-2012, 05:30 PM | #2370 |
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I don't think it's that complicated. A 3mpg drop is quite a bit, and a 3 mpg drop right after a fill-up while the temperature remains the same between fill-ups, kinda makes me think it's winter blend gas.
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11-19-2012, 01:24 AM | #2371 |
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Location: SF Bay Area, CA
Vehicle:2012 Impreza 2.0i HB |
That's what I've noticed in mild California during my last two tanks. There has been a noticeable drop in mileage with no other significant changes.
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11-19-2012, 07:45 PM | #2372 |
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South East
Location: Raleigh, NC
Vehicle:2012 Imp. Sp. Ltd. Blue/Silver |
Cold temps... Bah...
330.3 miles. 13.04 gal. 27 mpg avg. 25.3 mpg actual. 23 mph avg. 9625 miles on ODO. http://www.fuelly.com/driver/hemophilic/impreza |
11-19-2012, 07:51 PM | #2373 |
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NESIC
Location: MA
Vehicle:2012 Impreza Sp Prem 5MT OBP/DGM |
Same here. I've easily dropped about 3 MPG within the past few weeks.
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11-19-2012, 09:02 PM | #2374 |
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I monitored the water temperature via the Scangauge as the engine heated up this morning. When the interior of the vehicle was cold (at first) the engine would in fact slowly cool at stop lights. However, when the interior warmed up the Scangauge consistently read 182 to 184 deg F.
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11-19-2012, 09:48 PM | #2375 |
Scooby Newbie
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TXIC
Location: Austin, TX
Vehicle:2012 Imp Prm 5D CVT Dark Grey Metallic |
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