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Hello everybody,

I am the proud new owner of an outback XT Turbo and I understand the importance of putting high-octane gas in the turbo. But what happens let's say if a gas station attendant puts regular gas in by mistake even though the higher octane was requested? There was about a quarter tank of high-octane gas in so I got about three quarters of a tank of regular gas. 87 octane. Should I a get some octane boost from the auto store or be burn about half the tank and fill up with high-octane gas in mix the gases.

Thanks for the advice in advance

JMart
 

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Hello everybody,

I am the proud new owner of an outback XT Turbo and I understand the importance of putting high-octane gas in the turbo. But what happens let's say if a gas station attendant puts regular gas in by mistake even though the higher octane was requested? There was about a quarter tank of high-octane gas in so I got about three quarters of a tank of regular gas. 87 octane. Should I a get some octane boost from the auto store or be burn about half the tank and fill up with high-octane gas in mix the gases.

Thanks for the advice in advance

JMart
In a normal working car, the knock sensor will alter the spark timing to adjust to the lower octane.

It could take a few drive-cycles, after this tank is replaced with high octane, for the timing to revert back to the best adjustment for the high octane.

all this is designed to protect the engine, yet still take advantage of the benefit of higher octane fuel for the boosted compression of the engine. many people never bother with higher octane fuel, just use the mid/low octane stuff and live with reduced performance. There is some controversy about any overall savings in money.

I use high octane as suggested by the owner's manual.
 

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It’s really no big deal. Just fill-up with premium gas next time. You may lose some horsepower depending on the conditions as Subaru built in protections for people doing just that.
 

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Octane is not a measure of power or energy, it's a measure of volatility. High octane gas is less prone to preignition, in other words igniting before the spark plug does.

I've owned a few very high performance cars that couldn't care less if I ran regular gas, and currently ride a motorcycle that is downright stunning in the brute force department, and it is totally happy with regular. The XT will vary the timing but apparently not enough to compensate for what ever you pour into it.

In vehicles that say "premium recommended" I ignore it and have never had a single maintenance issue because of it. The XT says "required" so I roll my eyes and buy expensive gas.

On rare occasions when my car ends up with lower grade fuel I just keep my foot out of it. I put 1500 miles on my car two weekends ago and ran 89 octane the entire time. Got the best fuel mileage I've ever seen with it.
 
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