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2005 Forester 2.5X automatic
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5 Posts
Discussion Starter #1
I'm trying to boost my 21mpg on my 2005 Forester 2.5X AT. Just bought Pirelli P4's now, air filter is clean, new plugs any help? Thoughts? 75K mostly long haul highway miles.
 

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2012 Forester X Auto
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1,918 Posts
@michaelak -
MPG's are not the Forester's strong suit, since it is an AWD, relatively high profile vehicle.
If your car is a well maintained state, and the engine has decent compression, there aren't any magic cures...
…. unless you get a JC Witney catalog, where a few simple parts can give you triple the horsepower and give you 100 MPG's...
Note that your actual results will vary - A LOT.
Seriously..
You can get a minimum improvement with low rolling resistance tires, but how hard you press the skinny pedal will dwarf that effect.
About the only thing that works is to take off roof storage when you don't need it, keep your tires properly inflated and slow down.
At 60-ish my '12 gets over 30mpg. At 75 and over, I'm lucky to get 20.
That's just the way the car is.
 

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2007 Forester Sports XT 4EAT
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38,945 Posts
As noted by @DragonSubie7 the earlier Forester isn't overly streamlined... pretty much a box! :wink:

• Don't increase the tire footprint, as that will add to the rolling resistance.
• Run your tire pressure as high as you can, but not to where it overly degrading your ride comfort & handling. We run 36F/34R.
• Use the Subaru recommended 5W-30 engine oil.
• If you don't have a rear dust defector, don't add one!

My XT is tuned & I have a heavy right foot, so I've never bothered to check the gas mileage! :icon_eek:

Bobby...
 
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2019 3.6R & 98 Forester Atlanta, GA
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7,254 Posts
The Car Talk guys suggested this. Pretend there is an egg between your foot and the accelerator pedal and you are trying not to break it.
I'm unrepentant egg scrambler, a smiles per gallon guy.
 

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2005 Forester 2.5X automatic
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5 Posts
Discussion Starter #5
Thanks for the input, kinda what I thought...the Pirelli's helped me add 1-2 mpg, may try new plugs since it's been awhile...run synthetic 5w-30, so not many options to try...
 

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with my 08 xt, i was able to get 29.7 mpg in traffic. seriously as everybody be gentle with the pedal. I was also paying attention to the rpm when i got that number. i kept it under 2.5k.

Although now with boost gauge, its interesting how higher rpm without fully open throttle has less boost than lugging it in lower rpm. (still all under 0)

and as im typing this, is that how turbos work in eco friendly vehicles? the turbo assisting the engine 'suck' the air. Im usually not going above 0. which i suppose the engine is working less? curious thought
 

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2005 Forester Automatic
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495 Posts
If there are no codes, no CEL, then about all that might help has been discussed. Agree with plan for new plugs.

Another driving analogy that I have heard is "drive like there is a wedding cake in back"....

Mostly, speed and starts and stops are what kill.
 

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2005 Forester X and XT Manual and Auto
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940 Posts
I'm not suggesting this for the OP, but has anyone tried putting the 2WD fuse in and seeing if MPG went up at all? I personally wouldn't do it because i prefer to run the car the way it was intended (not to mention I would not be able to stand the AWD warning light on all the time) but for someone hell bent on MPG's I'm curious if this would actually add an MPG or two.
 

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2005 Forester X and XT Manual and Auto
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Yup i know it's meant to be a temp solution for donut or other needs but have heard of guys using it indefinitely to bypass center diff issues. 100% of power supposedly makes it to front wheels when used so it seems feasible one could squeeze an mpg or 2 out of it (regardless of whether the transmission might fall out in a years time or not).
 

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2007 Forester Sports XT 4EAT
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If you looked at that link I posted + all the links within that linked thread, you'll see many more disadvantages than advantages in making the Forester 2WD/FWD. No? :confused:

Example, I read this on a post:
The duty c solenoid is designed to get a pulsed on/off signal voltage. When you put in the fuse, you send 12v constant to the solenoid so it opens all the way. That constant signal is going to wear the solenoid out a lot sooner.
Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2004 forester sti
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2,188 Posts
you could try an injector cleaner or have your injectors clean and spray matched , what are your emissions like as they can tell a story.
im only saying this because it hasn't been mentioned.
 

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2012 Forester X Auto
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1,918 Posts
RE: Using 2WD only..
If you look around you can find tales of improved mileage, but since you can get the same effect (i.e. improved mpgs) by using the throttle sparingly, it is more likely that any observed FWD fuel use "improvement" is a result of the expectation for an increase in mpgs, and a driving habit change, rather than the change itself.

It applies to both medical trials as well as auto parts - Human nature is subject to the placebo effect.
If you believe that something you do to the car will improve your mileage, subconsciously, you will change your behavior to make that happen.
In the case of your car, all it will take is a little less right (or left - If you're Down Under) foot and a bit lower top speed and it happens.

Because most of the energy used is in accelerating the mass of the car up to speed and then overcoming wind resistance, neither of those two things change by overriding the AWD. It still takes the same amount of energy to move the car regardless of which wheels are powering it.

The other penalty of AWD is the weight of the additional running gear, which also doesn't change with the insertion of a fuse.
The extra differential and axels and transmission connections are still there.

Considering that there is some evidence to suggest additional stress on an internal solenoid could result in an expensive repair from FWD operation... Why do that?

If what you really want is a frugal 2WD car because you want great mileage, buy one.
It would be a better commuter car than a Forester for fuel use if you drive a lot.
Just don't plan on going to the same places and taking the same things that you can in the Forester.

My FWD 2013 Kia Rio routinely averaged 40 mpgs, but mileage isn't a major concern for me. I don't drive much.
AWD on the other hand isn't an option, because I have to go through snow or mud most of the year.
I drive a motorcycle more often than my car in good weather, and on it I do better than 50 mpgs provided I control my right wrist.
If I don't, I can easily drop that 50 to 40 or even 35 if the bike is being cranked *really* hard.

If you control your right (or left) foot you are more likely to see more mpg improvement than anything you do to change a car in good repair.
 
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