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I have a little confusion over current octane requirements or recommendations for the Crosstrek.
Here in eastern Oregon most gas stations give me three options 89, 91 or 93.
With my previous Subi, a Forester Turbo premium (93) was required, not so with the Crosstrek, I was told by the dealer that regular (89) would be perfectly acceptable, so I have been filling my '13 Crosstrek with regular, I have had no issues and seem to get very acceptable fuel economy so I guess my question is this, would changing to premium gas do anything for the car, performance or longevity for example.
Just curious, I was very excited about paying about 50 cents a gallon less than I had been for the Forester, but if I will see some benefit I would consider doing so.
Thoughts please.
 

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Premium will lighten your wallet but the weight savings when driving won't be worth it. Those are odd octane numbers. Regular is normally 87 in the USA except at high elevations when it is 85. 87 is all you needanywhere in the country. High elevations effectively lower normally aspirated combustion chamber pressures so 85 is all that is needed above about 5000 feet. You needed premium in the turbo because turbo or super charging raises combustion chamber pressures which creates more heat as well as pressure so more resistance to detonation is required. The Crosstrek engine is designed for regular and putting higher octane in won't improve performance. An engine has to be designed to take advantage of higher octane to get more performance out of it, like your turbo was.

The only possible advantage is if the additive package is inadequate with regular but that is very unlikely and guaranteed not to be an issue if you use a top tier fuel. Top Tier Gas
 

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More octane than needed is purely a waste of money. Follow the recommendations from Subaru. But, for longer, cleaner engine life, use a Top Tier brand of gasoline for a superior detergent package.
 

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I throw in a bottle of injector cleaner @ every oil change.
Better to do that on the tank just before the oil change, so the new oil is not affected by the fuel injector cleaner. Some leakage naturally occurs and you will carry around a slight oil deterioration until the next change. Techron is probably the highest quality product for cleaning the fuel system and should not be used more than twice between oil changes, but best just before fresh oil is installed. Run your tank to empty as can be. At the gas station, pour in the Techron first. Then add about 10 gallons of gas (assuming you left 1-2 in the tank to get there.) Drive that tank to close to empty and resume your usual filling cycle. If you happen to have Chevron gas, no need for this, as they make Techron and the gas already has some. Techron is the fuel system cleaner Mercedes Benz recommends.
 

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On my last car that only required regular fuel (2011 Ford Fiesta), I did actually see a benefit from using premium 91oct fuel. I consistently saw higher mpg, enough to warrant the added cost of about $0.20/gal. But not enough to warrant an additional cost of around $0.40/gal, as current prices show in my area.

With that said, I saw no benefit of running premium in the stock Crosstrek. None. 0.00mpg, no smoother running, no butt-dyno increase, nothing. And I was trying to find a reason to justify it. Now, however, I am tuned by Throttle Happy for 91oct. So I still run it.

So unless you're tuned, you'd be wasting your money.


But the one thing nobody factors in is how it makes you feel. Peace of mind is far more valuable than people give credit. If it makes you feel more comfortable, even if it's proven not to do anything, by all means do it. Because it's your car and it's your money.
 

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Better to do that on the tank just before the oil change, so the new oil is not affected by the fuel injector cleaner. Some leakage naturally occurs and you will carry around a slight oil deterioration until the next change. Techron is probably the highest quality product for cleaning the fuel system and should not be used more than twice between oil changes, but best just before fresh oil is installed. Run your tank to empty as can be. At the gas station, pour in the Techron first. Then add about 10 gallons of gas (assuming you left 1-2 in the tank to get there.) Drive that tank to close to empty and resume your usual filling cycle. If you happen to have Chevron gas, no need for this, as they make Techron and the gas already has some. Techron is the fuel system cleaner Mercedes Benz recommends.
Have you tried BG Products 44k? Fantastic stuff. But much more expensive.
 

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The sole function of higher octane fuels is to prevent pre-ignition in higher compression engines. Pre-ignition (knocking) can damage the engine over time. There is no need to use an octane higher than specified by the manufacturer. 87 is fine for the Crosstrek.

However, there is one type of fuel you may want to try. Gasoline in most areas of the country contains 10% ethanol. Ethanol has less energy than pure gasoline. You may want to see if any gas stations in your area sell "pure" (i.e., no ethanol) gasoline. That should boost your mileage. Try it for a while and see if it worth the extra cost. This is purely a mileage cost-benefit issue, so you may decide it isn't worth the hassle.
 

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NOTE: The active ingredient in Techron is PEA - polyetheramine - at anywhere from 20 to 49% concentration in the bottle depending on the version of the bottle you get - ie. 'concentrated' vs regular.

PEA is now also found in Shell gas as of a couple of years ago as well - ever since they started to advertise Nitrogen Enriched. Also, PEA is also found in other additives like the line from Gumout but as in the Techron line up, only some of the Gumout lineup has concentrations high enough to justify the cost.
 

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I have heard some people mention that knocking will still occur overtime with 87 octane in N/A subaru engines. Over long periods of time, this knocking wears out the head gasket much faster and can lead to premature failure. Many people only recommend 91 for all subarus to increase the life of your head gaskets. Any thoughts?
 

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The engine is designed for 87 however, this forum taught me that it's common to find 85 in high altitude. If I remember correctly, the air pressure changes the mixture in the cylinder and it bums like its 87 elsewhere; anybody?

However, use of 85 octane in high altitude is only valid for carbureted engines.

You can burn 85 in a higher rated octane engine but the car will try and compensate resulting in worse mileage and could possibly cause pre-detonation/uneven detonation (pinging, knocking) which makes for a very hot engine that can destroy plugs, pistons and cylinder walls.


Edit: I thought all engines were made in Japan (I know all our XV engines were) and for those in the IA plant, they assemble from JP manufactured parts, including engines. In other words, the NA engine is the same one you get in Australia or Europe.

Yup to below: The only time you need to switch to a higher octane is because you are already knocking: https://www.consumer.ftc.gov/articles/0210-paying-premium-high-octane-gasoline
 

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What will happen if I use higher octane gas than I’m supposed to?
A few things. For one, you will be wasting a huge amount of money paying for high octane gasoline. Second, your car will not run correctly, whether you notice it or not. Higher octane fuel requires more heat and more precision to burn correctly. If your car is designed to burn 87, it will not burn 93 correctly. Third, your gas mileage will suffer. The inability of your engine to burn the higher octane gas correctly will cause your engine to produce less power and thus will require more fuel to perform at the same level.
What about using lower octane gasoline in a high octane engine?
In this situation, you will see negative effects that could be even worse. Using low octane fuel in a high octane engine will result in severely reduced performance because the engine will attempt to adjust to the lower octane gasoline. In extreme cases, or with prolonged use of low octane gasoline in these engines, pinging or pre-detonation can occur and can eventually destroy your engine. Pre-detonation causes very hot conditions in your engine and can melt sparkplug and pistons.
What fuel you use in your vehicle is important. Make sure you always follow the manufacturers recommendations. Using a fuel other than what the manufacturer specifies will in no way help you save money, gain power, or do anything other than cost you money.
 

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What will happen if I use higher octane gas than I’m supposed to?
A few things. For one, you will be wasting a huge amount of money paying for high octane gasoline. Second, your car will not run correctly, whether you notice it or not. Higher octane fuel requires more heat and more precision to burn correctly. If your car is designed to burn 87, it will not burn 93 correctly. Third, your gas mileage will suffer. The inability of your engine to burn the higher octane gas correctly will cause your engine to produce less power and thus will require more fuel to perform at the same level.
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What about using lower octane gasoline in a high octane engine?
In this situation, you will see negative effects that could be even worse. Using low octane fuel in a high octane engine will result in severely reduced performance because the engine will attempt to adjust to the lower octane gasoline. In extreme cases, or with prolonged use of low octane gasoline in these engines, pinging or pre-detonation can occur and can eventually destroy your engine. Pre-detonation causes very hot conditions in your engine and can melt sparkplug and pistons.
What fuel you use in your vehicle is important. Make sure you always follow the manufacturers recommendations. Using a fuel other than what the manufacturer specifies will in no way help you save money, gain power, or do anything other than cost you money.
Sorry, the Knack, but the first part of your reply (using fuel with higher octane than the recommended one) is partly wrong.
According to my informations and also to my experiences it will not cause any damages to your engine, if you use fuel with higher octane than the recommended one by the car manufacturer.
In Germany the fuel with the lowest octane is Super 95 with 95 octane. In former times you could get fuel with 91 octane , named Normal, but that was at least twelve or fifteen years ago.
There also exists Super 95 E 10 containing 10 % Ethanol but also with 95 octane.
The next higher step of fuel you can get is Super Plus with 98 octane.
The fuel with the highest octane is offered by Shell - named Shell V-Power - and by Aral/BP - named Aral Ultimate - and they have 100 (Shell) or even 102 (Aral) octane.
In the German manuals for every Subaru model is recommended to use at least Super 95 or Super 95 E10 with 95 octane. Only for the WRX/STI is required at least Super Plus with 98 octane.
But in no, I repeat it, in no German manual for any Subaru model is advised against the use of fuel with higher octane than the recommended 95 octane (WRX/STI 98 octane).
And that's the same for all other car brands in Germany regardless of wether German, French, Italian, Japanese, Korean, American and so on. No car manufacterer advises or warns against the use of higher octane than the recommended one. It depends on your own decision as the driver , if you like to use any fuel with more octane than the required or recommended one.
You are right, that will damage your wallet but not at all the engine of your car.
With my previous Forester I've tested it for about 4 months to use only the priciest fuel Aral Ultimate with 102 octane.
Result: Neither the engine produced less power nor the gas mileage suffered as you state. For both matters it happened the opposite:The acceleration of the Forester was clearly felt being faster and the fuel consumption was 0.3l/100km lower with Aral Ultimate 102 octane than with Super 95.
But the underconsumption didn't compensate the higher costs of the fuel with 102 octane. Summarizing the use of Aral Ultimate was more expensive than using Super 95 and therefore I changed back to Super 95.

What you say about the use of fuel with less octane than the recommended one is right.
 

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I wish we could get higher octane fuel easily here. I buy 100oct in 5 gal containers for our track car.

I run 85 in our Forester that lives at 8500’ and 87 in our sea level XV & Forester.

I was chatting with the subie tuner in Barbados and he indicated that knock voltage isn’t seen like it is in the European cars. How does the Subaru handle knock?


Sent from my iPhone using Tapatalk Pro
 

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If it makes anyone feel better, it’s looks like it was a Google answer.

Fuel Octane, Choosing The Wrong Octane Will Cost You | What Could Be Greener

I used to get a high test gas every now and then. It won’t clean your engine any better but it felt like a little more power and higher octane does burn better.

Apparently, higher octane than required may improve performance and gas mileage and, reduce CO2 emissions if a vehicle is under heavy load, especially if in hot weather, but it won’t benefit normal driving. https://www.fueleconomy.gov/feg/octane.shtml


Basically what I’m reading from GMork is that the local Subaru Corp uses the lowest level appropriate for the engine that’s available in the country. Can you imagine if the DE manuals said 87?
 

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Following the Chinese saying "Who asks is a fool for five minutes - who does not ask remains a fool forever" I ask the question:

What are "DE manuals"? :icon_scratch:
 

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Lol, sorry the ISO 3166 code for Germany.

DE= Deutschland
CA = Canada
US = USA
FR = France
And so on.

62846A4E-3BF7-4253-A775-D5F12EADE4B5.jpg
 

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My answer was also Google, and was repeated on multiple sites. I am a computer techie by trade, not an engineer. I have read the same over the years though, that a higher octane than the engine is designed to run can also damage the engine over time as it does not burn properly, and that there is absolutely no benefit gained from running higher octane. As far as the German XV, I'm sure the engine must be designed to run the higher octane if that is all that is available there. Even the models available between countries vary.
 

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Lol, sorry the ISO 3166 code for Germany.

DE= Deutschland
CA = Canada
US = USA
FR = France
And so on.

View attachment 272090
Oops, you sometimes do not see the forest for the trees. :icon_redface: :icon_lol:
Of course I know "xxx.de" as designation for German websites or email addresses. But I didn't realize you used DE as ISO designation for German.

To your question itself
Can you imagine if the DE manuals said 87?
Nobody would care about that in Germany because the fuel with the lowest octane has 95 octane and excels already a requirement of 87 octane.
 
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