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I bought my first Subaru Saturday (2018 Outback) and am looking to trade the tires for something a little more aggressive. I also plan to DD the car and will put on around 80 miles per day for work and don't want to kill my MPGs. Has anyone who upgraded to 235s experienced much different in mileage, and if so how much?
 

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2016 2.5i Outback, 2002 Audi S4 Avant, 1980 CB750F Supersport, 1985 Carrera 3.2
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568 Posts
I had 245/65r17 K02's and saw about the same 5 mpg drop. I have since switched to a 235/65R17 Pirelli Verde All Season and it's gone up about 2-3 mpg so far on average (or about 2-3 mpg drop). Granted this is on 17x8 wheels as well, so rotating mass has increased from the stock setup.
 

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2016 3.6 Limited with ES
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3,152 Posts
I'd almost suggest a bigger bang by upgrading the RSB and adding 85d bushings, but then again, I drink a little too.
 

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OBW H6 VDC, Tribeca, XT6
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there's quite a few factors and in some cases larger tires can improve gas mileage, i usually see it on highway driving, which at 80 miles per day may be a consideration.

1. tire brand and style could impact more than size. you're changing more than one thing at once so that complicated things -the size and tire type "aggressive", both may impact mileage.

2. if you're in a city area and aggressive driving and dancing on the gas pedal then larger/heavier tires have a greater chance of denting the mileage as the engine constantly accelerates that heavier mass and increased diameter.

3. larger diameter tires can do better on highway mileages and worse on in town driving. the tire "goes further" for each revolution. there's a limit and it depends on vehicle, driving, and other tire changes (width and tread type may also impact mileage). i've gotten better highway mileage with larger tires many times, but usually worse in town mileage. and it's not going to work that way if the tires are heavy, sticky, aggressive, wider, etc and again depends on driving.

mountain verses flat land driving makes a difference too. i find the larger tires can change when the car wants to shift and mileage in the mountains more than flatland.
 

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Brucey
'17 3.6
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13,359 Posts
I think it's several factors for such a big penalty.

Going from Low Rolling Resistance to Normal tires is a hit.

Going from Normal Tires to All Terrains is a hit.

Going from All Terrains to LT All Terrains is a hit.

Going up in weight is a hit.

Going up in size is a hit.

Which I'm doing ALL of this at once switching between my summer 18's to the 245 KO2's on factory wheels.

Weight alone goes up nearly 20 lbs per tire.

It's why I don't run them all summer and have considered going with a better compromise summer/all terrain tire.

As it is now I have 3 sets of wheels/tires to get around all the issues with each set.

The 3.6 also takes less of a hit when doing this. With the KO2's on mileage is very similar between the 2.5/3.6.

But I'm not going to start into a 3.6 debate.
 
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