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So I have just at 390 miles on the car, or about 1 tank. I know new engines are tight, but so far, I have to say the mileage is not even close to the sticker. I have been following the break in procedures and haven't revved the engine over 4k, no jackrabbit starts....haven't really driven more than 5mph over posted speeds and no extended idling time. About 70% of the driving has been highway, not stop and go. So far, hand calculated, I am averaging 14.9MPG.

Is this a known issue with Subaru that the engines show poor MPG during break in? I get it, but less than 15 seems on the low side. The instant calculator (not accurate I know) seems to range from 17 to mid 20's....with a few high and low spikes. I have 2 friends with Ascents and both are above 25MPG on average.
 

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2019 Ascent Touring (CWP)
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There are plenty of threads on fuel economy in the relevant forum discussion areas. There are some folks/some vehicles that for some reason have lower fuel economy performance that most. Some of that is driving style; some is environmental and some is just that particular vehicle. If you live in an area where the weather has turned cold, that's going to affect things, too. Give it some time if you've only put one tank of fuel through. And keep your revs below 2500 as much as possible.
 

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Only averaging 22.6 on my Ascent. Disappointing since I was averaging 33 on my Forester Sport
Compare the weight and size... These are not comparable vehicles when it comes to fuel economy. We have both an Ascent and a Forester so I know that from experience.
 

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So I have just at 390 miles on the car, or about 1 tank. I know new engines are tight, but so far, I have to say the mileage is not even close to the sticker. I have been following the break in procedures and haven't revved the engine over 4k, no jackrabbit starts....haven't really driven more than 5mph over posted speeds and no extended idling time. About 70% of the driving has been highway, not stop and go. So far, hand calculated, I am averaging 14.9MPG.

Is this a known issue with Subaru that the engines show poor MPG during break in? I get it, but less than 15 seems on the low side. The instant calculator (not accurate I know) seems to range from 17 to mid 20's....with a few high and low spikes. I have 2 friends with Ascents and both are above 25MPG on average.
Same here … we have been getting 14 mpg in the city. It must go to the service shop. The more of us doing it the better. Maybe Subaru will wake up and understand that Ascent is a big turd when it come to mpg.
 

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It is a large, heavy car. Noticed when the temps were reading 100 degrees last month (purchased it on Labor Day) the mileage was low, 19mpg. In the evening when the temps cooled and also in the past week the mileage has gone up to 21mpg. I think the AC has a lot to with mileage in hot climates, being that the engine is small. Never had such a fluctuation in mpg with the 3.6 Outback with the AC on, or fluctuation in oil temp for that matter. The Outback got approximately 22/27 city-highway.
 

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2021 Subaru Ascent, 2015 Kia K900
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My Ascent has 4,000 miles on it. If I replace the factory filter with a K&N filter which help with mileage will that void the warranty?
Using a K&N filter won't void your warranty. Before you get one, have a look at this comparison test. The K&N filters let a lot of particles through that the paper filters don't.

 

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An aftermarket air filter isn't going to affect your mileage or horsepower. Even aftermarket CAI (on vehicles that can be equipped with them) don't do much for most vehicles these days because the OEM air intake is already designed that way with modern engine and injection systems.

But I'll reiterate the previous poster's statement: US law does not permit a vehicle manufacturer to "void a warranty" when one chooses to use aftermarket parts. The only thing they could do is deny a warranty claim for something when they can prove it was actually caused by said aftermarket part(s) and even then, everything else remains under warranty for the duration of said warranty.
 

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My Ascent has 4,000 miles on it. If I replace the factory filter with a K&N filter which help with mileage will that void the warranty?
My 2021 Ascent has about 8,000 miles and the mileage has gone up overall. Started off at 22 mph and now its 24 mpg. I am less aggressive when I take off from a standing start and more light footed. Hopefully the mpg will climb a little more. Besides mpg I have been very happy with the vehicle.
 

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2022 Ascent Onyx, Ice Silver
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Using a K&N filter won't void your warranty. Before you get one, have a look at this comparison test. The K&N filters let a lot of particles through that the paper filters don't.

+1^^

When I owned one, I frequented the Ford Diesel Truck site. I recall several posts of guys who "dusted" their engines using K&N or similar reusable, oiled filters. Turbo engines create more vacuum than normally aspirated ones and will eventually suck much of the oil from the filter media, allowing more particles thru to the turbo blades and eventually the cylinder walls.

I won't use them on any of my engines, YMMV.
 

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So I have just at 390 miles on the car, or about 1 tank. I know new engines are tight, but so far, I have to say the mileage is not even close to the sticker. I have been following the break in procedures and haven't revved the engine over 4k, no jackrabbit starts....haven't really driven more than 5mph over posted speeds and no extended idling time. About 70% of the driving has been highway, not stop and go. So far, hand calculated, I am averaging 14.9MPG.

Is this a known issue with Subaru that the engines show poor MPG during break in? I get it, but less than 15 seems on the low side. The instant calculator (not accurate I know) seems to range from 17 to mid 20's....with a few high and low spikes. I have 2 friends with Ascents and both are above 25MPG on average.
I just bought a 2022 and have only filled it 3 times. I am also having a hard time getting it to average over 15mpg its at 14.5 right now. I have a fairly flat commute to work 2 lane country roads very little stop and go. If not better by the 1k mile mark ill address it with the dealership.
 

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2022 Ascent Onyx edition, Autumn Green Metallic.
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Maybe instead of babying mine when it gets delivered, I'm going to do what I have always done with other brand new cars, drive em like I stole em. I have always had great cars by doing so. Good power great milage and no engine problems.
 

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2022 Ascent Onyx edition, Autumn Green Metallic.
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The breakin procedure for Subaru is ... in the manual.
 
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