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2020 Onyx
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However, as with anything, go buy whatever you want! If it makes you feel better and reduces stress, then go for it!
It does make me feel better and reduces stress. I don't want to add aftermarket additives and would rather have it in the gas from the pump. It would be one thing if it were contraindicated for reasons other than cost. If it's only money, then it's not a barrier. It's not like I'm buying ten dollar a gallon 100 octane. It's just premium fuel at a local gas station a few miles down the road, located a few blocks from the Subaru dealership.

For some people it's well worth it to pay a thousand dollars for paint protection film, or have pin stripes painted on, or get nice wheels. To each his/her own. For me it's premium fuel, frequent oil changes.
 

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Just got a new Outback 25 miles on it so far. I traded in my 2011 Forester. Both manuals say use 87 Octane. I live in New Mexico at 6000 feet. In New Mexico you can get either 86 or 88 octane. When I used 86 Octane in my 2011 it caused problems with the O2 sensor requiring rebooting the computer this happened several times. I then switched to 88 Octane and problems stopped. The Subaru salesman in Albuquerque said the Outback will run fine on 86. Opinions please.
 

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2020 Subaru Outback Limited
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613 Posts
If the owner's manual doesn't say "87+ except for over X feet...". Then I would go with 87+ to keep my warranty intact.
 
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2020 Onyx
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Salesmen are not technical experts and will say whatever they think will make you more likely to buy the car, like saying you can use cheaper fuel.

I agree with @andrew25 that you should be a stickler when it comes to adhering to the manual's fuel requirements for 87 octane or higher. While it may not be in the manual, I'd also use top tier fuel if available near you.
 
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SubaruOutback.org Founder
2021 Outback Limited 2.5L - 🍦The Ice Cream Man🍦
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Why not experiment for yourself? When I owned my 2003 Outback H6, which recommended 91 octane gas, I tried every octane from 87 to 94 to see what difference it might make. It would run okay on 89 but anything less would cause the check engine light to come on. I came to find out that the higher the octane the better it ran, it seemed to like Shell V-Power 93 the best.

You ain't gonna hurt nuthin' puttin' 86 octane in the tank, the worst that will happen is that you might get a check engine light that will resolve itself by putting higher octane gas in as replacement.
 

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2020 Subaru Outback Onyx XT
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This is my first time ever owning a turbocharged car. I bought the 2020 Onyx XT new and I had no idea about fuel types. Nobody at the dealership ever once mentioned the car only uses 87 octane fuel. I live in Colorado at 6,000 ft elevation and I have put 85 octane fuel in the tank 5 times now and the car now has about 2,000 miles on it. I havent had a single issue (loss of power), heard any pinging, or any backfires. The manual only says 87 AKI as the fuel type. May I have ruined my new engine?
 

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2021 Outback Limited 2.5L - 🍦The Ice Cream Man🍦
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If there is an issue with the octane level your check engine light will come on. I had a Subaru that "recommended" 91 octane gas that would get a check engine light if you put 87 octane gas in it. 89 octane gas didn't cause a check engine light but the powertrain was noticably more sluggish.

I would just recommend going back to 87 octane gas in the future. You are free to use higher octane fuel in this engine if you so choose.
 

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2020 Outback Limited XT Black on Ivory
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Wow, I didn't even know you could still get 85 octane.....Threat it to a tank or two of 91 and enjoy the ride ! 😊
 

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2020 Outback Onyx XT, 2007 Outback 2.5
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Octane, turbos, and altitude make kind of a weird dance. Subaru makes a big deal about 87 octane regardless of elevation because the turbo normalizes combustion pressure — e.g. the turbo is putting out higher pressure at higher altitude and lower pressure and low altitude (I don’t think anyone has confirmed that this is true). So by that logic, which is backed up in the manual for whatever that is worth, the octane you need at sea level is the same as at altitude.

As ever, it’s your car and you have some choices. For now, I’m running 91 mostly because 91 generally has more detergents. Some people have suggested that is important for this engine. To be honest, I don’t understand why. Also 91 from Costco is about the same price as 87 from most gas stations. When I start piling on mileage this winter, that choice may change. Something you might consider is run two or three tanks at each octane level and see if you can spot a difference is performance, smoothness, and fuel economy. I’ve had cars in the past that only need 85, but there was a big enough mpg difference between fuel grades to offset any cost difference. If you do decide to run 85, I would strongly consider filling up with a higher octane gas if driving to lower elevations. 85 may be fine at your house, but it may not be fine when you drop a few thousand feet on a single tank. The last option, which is more related to your vehicle history and less to the specific topic is I think COBB has a minor tune available for the engine. If you have to feed the car higher octane fuel anyway, it might be something to consider.
 

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2020 Onyx
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It is not compatible with the 2020 Outback XT yet - Cobb is supposedly still working on it.
 

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2020 Legacy Premier GT & 2007 3.0R Outback LLBean
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I have been told by two different mechanics that changing octane levels every few tankfuls is more detrimental than sticking with one octane level.
 

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20 Outback Premium; former 19 Outback Premium, 85 GL Wagon, 87 GL-10 Wagon
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Does the engine also compensate for higher than recommended octane - example 92?
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As in more power? I don't think so. 85 octane is pretty common at higher elevations as well as some states in the midwest. I'll confess to using it without incident in our 2.5 when traveling. Most of the places we frequent, other than the higher elevation areas, have 87 as the lowest available, so we don't encounter 85 very often.
 

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Maybe this helps:

The EPA says on their website, “The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower—because it was cheaper and because most carbureted engines tolerated it fairly well. This is not true for modern gasoline engines. So, unless you have an older vehicle with a carbureted engine, you should use the manufacturer-recommended fuel for your vehicle, even where 85 octane fuel is available”.
 
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