87 octane in DI turbo blessed by manufacturer?

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Subaru authorizes the use of 87 octane regular unleaded in the 2.0 liter Direct Injection twin scroll turbo engine in the 2014 and newer Forester XT's. Granted, they say you won't get rated fuel economy nor will you get the rated 268 hp. Over on subaruforester.org someone posted correspondence from Subaru Canada confirming it will not void warranty either. 91 octane or above premium is shown as "recommended" not "required."

I am looking at new XT's at the moment, is why I took notice of this most unusual situation.

I find this fascinating, they must really have that engine sorted.
 
Same with the new VW 1.8tsi DI....87 from the factory. APR did dyno testing and the car lost power with 93 octane.
 
The Ford 3.5EB loses about 10% of its horsepower using 87 versus 91 according to some tuner sources. However, it still runs just fine. I've run 87 sometimes in the winter, but always switch back to 91 always for the spring/summer/fall.
 
My Sonata is the same way. Hyundai claims the car will produce 10 more HP on premium gas. I used 87 for the first 10k miles, then switched to 93. No more hesitation under heavy acceleration, but it could all be in my head.
 
The computers just adjust, most modern cars made in the last decade or so will do this.

You do realize that most of those leased BMW and Audi's with high compression and boosted engines run their entire 36 month lease term on whatever gas is cheapest?
 
Originally Posted By: hattaresguy
The computers just adjust, most modern cars made in the last decade or so will do this.

You do realize that most of those leased BMW and Audi's with high compression and boosted engines run their entire 36 month lease term on whatever gas is cheapest?


Lol, I never thought of that. Good point.
 
Originally Posted By: lyle
The Ford 3.5EB loses about 10% of its horsepower using 87 versus 91 according to some tuner sources. However, it still runs just fine. I've run 87 sometimes in the winter, but always switch back to 91 always for the spring/summer/fall.


The rated horsepower is with 87 octane. The engine does gain horsepower (I've been told about 20 hp) with 91 octane.

Here is what the owners manual says...

Your vehicle is designed to run on regular fuel with an octane rating of 87 or higher. For best overall performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel will be most noticeable in hot weather or in severe duty applications such as towing a trailer.

Computer controlled engines will retard or advance the timing to adjust for octane rating.
 
Wow that's pretty awesome of Ford to use 87 for the official published hp and tq ratings and let owner's get even better by opting to use premium when they want.

I've just always gone by the Old School rule that forced induction requires premium.
 
It's not just turbo engines. My 3.5 V-6 Challenger gets 2 mpg better consistently with 89 octane. (92 premium doesn't do any better than 89, though. I average 24mpg with 87 and 26 mpg with 89 in my daily driving with about 60/40 highway/stop & go.
 
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