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00 Outback wagon 03 VDC wagon 18 Touring 3.6 white
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Discussion Starter #1
Hello:

My 2000 Outback wagon 2.5 pretty much knocks under any kind of load. I use 89 octane gas (It's worse with 87 slightly better with 93). Is this unusual for this engine? During the winter my fuel mileage drops from almost 29 mpg to 23 mpg. This seems like a large variation. I have heard that changing the thermostat might help this. Any one done that with good results?

THanks
Bob
 

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Formerly 04 Outback 3.0R VDC, now 2011 Mitsubishi Pajero GLS DiD
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1,617 Posts
Have you tried resetting the ECU? I'm sure there are instructions here if you search for it. You should always use at least the octane that Subaru recommends, higher should be better. If you live in a very cold climate the winter fuel may have a very different composition to the summer fuel and be less efficient.
 

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SubaruOutback.org Founder
2018 Outback Limited 2.5L - 105,000+ miles
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5,120 Posts
BOBOBW said:
Hello:

My 2000 Outback wagon 2.5 pretty much knocks under any kind of load. I use 89 octane gas (It's worse with 87 slightly better with 93). Is this unusual for this engine? During the winter my fuel mileage drops from almost 29 mpg to 23 mpg. This seems like a large variation. I have heard that changing the thermostat might help this. Any one done that with good results?

THanks
Bob
Okay, you said you normally use 89 octane. I think may be your problem as most 89 octane fuels use 10% ethanol, its not good to put corn in your car ;) I'd say to just buy the cheapest 91 (or higher) octane gas you can find, either that or do like I and many other do and get a gasoline credit card. That is one that the gas stations offer in which you can get a 3% or so discount on gas by using it. I recommend BP/Amoco, Chevron, or Shell by whatever is most available in your area.
 
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