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Hi,

After some time off test driving different cars and considerations I finally settled on the Impreza which I should pick up end of the week.

But I'm still wondering why the S model had higher fuel consumption (in the specs)?

It's exactly the same engine. So the only thing I can thing of its the width of the tyres that would add some rolling resistance.

But the difference seems quite big for that.


Any reasonable knowledge on that?


Thanks.
 

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My Limited Trim is nearing the completion of the break in period (1000 miles). The mileage is about 24 mpg and at least 600 miles were on the highway.
 

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It's the rolling resistance of the 18" tires, which are wider and softer, combined with more air drag for the same, and now throw in the greater rotational mass.
 

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Heavier wheels and tires hurt city mileage, wider tires hurt highway mileage. Many people are surprised when they upsize wheels and tires that their car is slower
 

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It could be that the Sport models all come standard as manual. I don't know about weight for sure, but i really doubt that wheels are gonna make that much difference. I added a screenshot of the difference, I could have sworn it was worse on Subaru's website at some point.
 

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Aren't the steel wheels of the base (most efficient) heaviest of all?


The Sport and other trims have 150lbs or so more curb weight, probably from the addition of features like a sun roof, more sound deadening, acoustic windshield...


Final drive might be a little "taller" as well, more effort required to get up to speed.
 

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Get's better after break-in, with higher mileage.
2018 Sport, 12,800 miles
I usually get better mileage commuting, between 33 and 36 mpg weekly average.
Last fill up yesterday morning, 390.9 mi/11.67 gal=33.49 mpg.
[This includes legal passing, inspired cornering and playing around turns]

You should get even better mileage if you have a CVT.

previous post:
I drive a mix of city, back roads and highway.
2018 Impreza Sport hatch 5sp, now has 8K miles.

Fill gas tank specs
for the last 6 weeks:
8/7 = 35.75 mpg
8/1 = 34.02 mpg
7/26=32.32 mpg
7/20=34.19 mpg
7/16=32.50 mpg
7/11=33.35 mpg
Note: average mileage includes using AC this summer
 

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I was going to suggest that the roof-rack will also reduce MPG.... but that is only a factor on the "Limited" models.

Perhaps the "ground effects" package (although it APPEARS more aerodynamic between the front/rear wheels) is also impacting MPG.

As far as wheel-weight is concerned, in the drag-racing world, every pound shed from a spinning wheel is equivalent to about 8 lbs of static weight. This is due to centripetal forces on a spinning mass. (spinning a bicycle wheel takes MUCH less force than equivalant-diameter car wheel) This is why the front wheels of a drag-race car are VERY skinny and light.
 

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I was going to suggest that the roof-rack will also reduce MPG.... but that is only a factor on the "Limited" models.
I think that was tested on Myth Busters and found to be false.

As far as the larger rims and tires adding rolling resistance and weight that is a given, but they look better and help the car handle better and that is all I care about.
 

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As you move weight further away from the centre of the axles you require more energy/power to move them. Even if the weight of the wheels are the same or less, larger wheels sap power.

Right now on my weekly 4 hour highway drive I am getting 34 mpg's (US) ( 6.8 L/100 kms metric). 2020 Impreza Sport Tech. This is at 70 mph, cold winter temps (-5 degs C) and running crappy winter blend fuel (known to kill fuel economy). This is the exact same fuel economy I get with my 2019 WRX Sport on the exact same trip and same conditions. It is a bit better than my 2017 Honda HR-V with its 1.8L motor and AWD.

I'd like to see my Impreza improve a bit more, just passed 1000 miles break-in. I am just comparing it to my WRX, but my WRX gets phenomenal fuel economy, better than expected. Glad that my Impreza beats my Honda HR-V so that is good, and it drives a million times better.
 

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2019 Subaru Impreza Sport 5 Dr. Manual Shift
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When I saw the title the first thing that came to mind was the wheel weight.

Math warning > This is a cool excel sheet regarding wheel weight you can DL from my google drive here >Click Me<

Fun to mess with if you are curious.

Screenshot:

22898
 
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