We’ve written extensively about the Subaru Outback, its capabilities, and various features on this blog. Today, we will talk about what fuel this sedan needs and what fuels are strictly prohibited. Let’s start with a quick answer:
Subaru Outbacks manufactured before 2009 use regular unleaded gasoline with an octane of 87 (2.5L non-turbo) or 91 (3.0L and 2.5L turbocharged). After 2009 all Outbacks started using regular unleaded gasoline with an octane of 87.
However, that doesn’t tell the whole story. Below we’ve outlined recommendations and requirements for different kinds of fuels and fuel additives. We’ll also go into detail about the compatibility of the Outback with oxygenated blends. Furthermore, we discuss the tank size of these generations. Read on!
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Fuel Requirements Per Generation
- Subaru Outbacks manufactured between 1998 – 2009 with a 2.5L non-turbo engine make use of regular unleaded gasoline with an octane of 87. For the 3.0L non-turbo engine 91 octane is recommended although 87 octane can be used temporarily. For the 2.5L turbocharged engine 91 octane is mandatory and 87 octane should not be used.
- Subaru Outbacks manufactured between 2009 – Present-day use regular unleaded gasoline with an octane of 87 for all engine types.
Now that you have a clear image of what fuel you should use with which model year and engine type, it’s also important to talk about premium gasoline. This is because many people wonder whether or not premium gasoline isn’t a better choice overall, even for the engines for which regular gasoline is recommended.
It’s essential to know that premium gasoline (with an octane of 91 or higher) is only helpful for engines designed for this fuel. Higher octane fuel does not give the Outback any performance or durability benefits if the engine is not designed for premium gasoline.
Instead, you’ll be paying for more expensive gasoline that does not do anything special for your car. Therefore, it’s recommended you stick to the guidelines mentioned above.
Furthermore, using regular gasoline where premium gasoline is recommended will damage the engine and the fuel system. More on that in the subheading ‘Knocking Of The Engine After Refilling’ that you’ll find below.
Also read: The Exact Bolt Pattern Of A Subaru Outback
Another topic we’ll need to talk about is the use of reformulated gasoline. Reformulated gasoline is gasoline that’s designed to burn more cleanly compared to regular, non-reformulated gasoline. This kind of fuel first became mandatory in California but is currently compulsory in more than 19 states/regions in the United States. Especially areas where the air quality is considered poor have rules regarding the use of reformulated gasoline.
It’s good to know that reformulated gasoline is 100% compatible with all the Subaru Outback generations. Subaru recommends the use of this fuel whenever it’s available. Also, you’ll get the same fuel economy compared to regular non-reformulated gasoline, and you won’t have to carry out any extra maintenance.
Oxygenated Blends Such As E-85
Besides reformulated gasoline, some types of gasoline have ethanol, methanol, or MTBE mixed into them. It’s important to know that these fuels are compatible with the Outback, although you’ll have to keep a close eye on the percentages used in your fuel. The guidelines are as follows:
- All generations of the Subaru Outback can use fuel with methanol although the fuel should not exceed a maximum of 5% methanol. Also, the fuel should be accompanied by sufficient quantities of the proper cosolvents and corrosion inhibitors required toprevent damage to the fuel system.
- Subaru Outbacks manufactured before 2019 can use fuel with a maximum of 10% ethanol (E-10), E-15 and E-85 are therefore not allowed. Outbacks manfuctured after 2019 can use fuel with a maximum of 15% ethanol (E-10 and E-15) but E-85 is not allowed.
- All Subaru Outbacks can use fuel with MTBE although the fuel should not exceel a maximum of 15% MTBE.
Not keeping to these guidelines will result in engine knock (more about that in the subheading below), the check engine light coming on, and the vehicle reducing speed to prevent heavy damage.
Gasoline With Additives
Online, many additives are available for the fuel of your Outback that, according to their advertising, help your car reach peak performance or increase the durability of the fuel system and engine. Subaru strongly advises against the use of these fuels for the Outback.
The reason for this is that some additives will contain silicon or metallics that will damage the engine and fuel system when they are used. Damage that’s caused this way does not fall under the warranty of the vehicle.
Instead of using additives, Subaru advises you to stick to the guidelines we’ve given so far in this article regarding the quality of the fuel. Furthermore, it’s recommended you only buy fuel from certified TOP TIER gas retailers. These retailers can be found via toptiergas.com.
TOP TIER gas contains all the necessary additives for your Outback. This will help the car reach optimum performance while simultaneously cleaning the engine of possible deposits.
Knocking Of The Engine After Refilling
In some cases, you’ll hear a knocking sound coming from the engine. If this is a slight knocking sound, please know that this is entirely normal. A slight engine knock may be heard, especially when the engine is performing at or near-maximum capacity.
However, a problem does occur when this knocking sound becomes louder and louder. Especially if you just refilled your car, you may have a significant problem. In this case, you’ve likely used fuel with a lower than recommended octane rating.
If you hear a loud knocking noise, it’s recommended that you stop the car immediately and contact your dealer. Your car likely needs to be drained of the fuel you’re currently using. Furthermore, the fuel filter will need to be replaced, and the car’s memory will need to be reset by disconnecting and reconnecting the battery.
Also read: 9 Troublesome Problems Of A Subaru Outback
Fuel Tank Size Subaru Outback
- Subaru Outbacks manufactured between 1998- 2009 have a fuel tank capacity of 16.9 gallons (64 liters).
- Subaru Outback manufactured between 2009 – Present-day have a fuel tank capacity of 18.5 gallons (70 liters).
Hi! My name is Stefan; I’m the owner and lead writer at TheDriverAdviser.com.
I’m an active writer on this blog myself, as well as a novice car mechanic. For the really technical stuff, I find writers with experience as a mechanic or who have studied mechanical engineering.
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