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Guest Message by DevFuse

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What engine maintenance can i do to improve fuel consumption on a Forester SF5 2000

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6 replies to this topic

#1 MOcen



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Posted 20 March 2014 - 11:51 AM

I have changed my spark plugs to iridium however my fuel consumption is still high.I have just acquired the car and it has done 130,000KM.

Edited by MOcen, 20 March 2014 - 11:53 AM.

#2 Fairtax4me



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Posted 20 March 2014 - 05:33 PM

How bad is it?
You should be able to get around 24-28 mpg. 10-12 km/l

Poor fuel economy can have several causes. Dirty air and fuel filters. Worn spark plugs, old/clogged PCV valve, dirty/clogged fuel injectors.

Low tire pressure, incorrect tire size, or sticking/dragging brakes will hurt fuel economy as well.

#3 MOcen



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Posted 21 March 2014 - 12:38 AM

My full tank is doing about 350Kms.Its doing about 5-6 Km/L.


I did also change my tires from the original 205/70/R15 to 215/70/R15.The new tires are taller and am starting to get worried they slowed the car abit thus affecting the fuel consumption negatively.


I did service recently and changed the Air Filter,I was also thinking of changing the fuel filter to a new one soon hoping to get better fuel economy.


Please advice should i go ahead and switch the tires to 215/65/R15 these seem normal height and make the car more stable.

Edited by MOcen, 21 March 2014 - 12:55 AM.

#4 1 Lucky Texan

1 Lucky Texan

    I read a lot about Subarus. '03H6OBW,'06WRX

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Posted 21 March 2014 - 08:15 AM

changing the tire diameter away from stock will affect the odometer (and speedometer)n by a few percent. The math for mileage will be affected. For instance, larger tires means you've gone farther, and gotten better mileage, than the odometer indicates. But, it may be possible to get good calculations using GPS readings.


 a bad Engine Temp Sensor may not create a failure code/check engine light but cause the car to run 'rich'.


The ECU also stores the Fuel Trims. If those can be retrieved with a scan, it may offer some clues at to whether the ECU is reacting to a failing sensor by pumping in more fuel.


Remove as much weight from the car as possible. Do not carry tools or any other gear you don't need.

Edited by 1 Lucky Texan, 21 March 2014 - 09:22 AM.

#5 presslab


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Posted 21 March 2014 - 09:18 AM

Check the toggle rate on the upstream O2 sensor.  Or if that's too complicated you can just replace it with a new one.


Do the tires wear funny?  Check wheel alignment and pressure.

#6 robm


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Posted 21 March 2014 - 11:34 AM

5-6 km/L is really bad.  Is this short trips around town, or on the highway, warmed up?


O2 sensor is a good bet, and fairly cheap.


Sticky brakes?  Check how warm they are after driving normally for a few miles.  Check if one wheel is hotter than the others.  Fronts are usually warmer than rear brakes.


Is the air conditioning working overtime? 

#7 MOcen



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Posted 22 March 2014 - 12:50 AM

5-6km/l is on the short trips,I have not been on a highway with it.I will also check out the brakes and see if they are sticky.


My air condition is not working overtime,I use it once in a while. I will go ahead to replace my 02 sensor,we do have an NGK distributor in the country where i will buy one.



My tire pressure and wheel alignment are fine i did them recently when i bought new tires.I will have a mechanic look at the Engine Temp Sensor.


Let me replace the 02 sensor,Fuel Filter and check the brakes too.I will keenly observe the fuel consumption after these repacements.


I appreciate all the expert advice and tips you have given me so far.




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