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Hello all, new to Subaru’s but I’ve owned and maintained many vehicles. I recently purchased a 2003 Subaru Forester 2.5X as my beater daily for work. 100,000miles on the engine. The whole reason I bought it was because I needed something with decent space and decent MPG, and the previous owner (I know, can’t be trusted but still) claimed he got around 300 miles on a full tank. After driving it for a whopping 70 miles I’m now reading a half tank. I realize they’re AWD and don’t get amazing gas mileage, I’ve owned other AWD vehicles, but at this rate I know something has to be wrong. I don’t smell any fuel leaks, but I haven’t ruled that out either. Any help/recommendations regarding the situation or what could be wrong would be greatly appreciated. Overall the car runs great super smooth thats why I’m stumped. I’ve never seen a literal 50% decrease in gas mileage in anything I’ve owned.
 

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2001 Forester
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How fast did you drive it at 70 miles distance? If you drive this vehicle with a lead foot, ie hard on gas and hard on brake, it's drinks the fuel. Driving at 70+ mph, keeps this engine revved up to 3000+ RPM so it's going to suck up fuel.

So how fast did you drive? how hard are you braking?

have you looked at the spark plugs, air filter? Are any of the brakes dragging? What about tire pressure? What kind of tires? Large/wide AT tires will hurt MPG. Roof rack? Extra weight in the back? have you tried even filling up the tank and then calculating miles vs gallons after the fill-up? Making your judgement based on fuel gauge is not accurate.

But yes, if you feather the peddle and drive lightly with little stops and start, you can get 300 miles to the tank.
 

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This is quite literally a YMMV sort of thing.

Let's say the "300 miles per tank" equates to just about 20 MPG (assuming he didn't run it dry all the time). Hell, the fuel light in my wife's old '08 would come into almost exactly when there was just over two gallons left. Trip B on the odo was reset every fill up and I told her that 300 miles was about as far as she should push it which should have left about 20 extra miles wiggle room.

Personally, I would start keeping a log between fill ups. Get the real MPG numbers based on your driving style, etc. Make note if those miles were mostly in town, hwy and so on. Only then can you get a reliable gauge on what range you can expect.

I'd also do the stuff suggested bman with a tune up (if needed), checking tire pressures, etc. Just remember that city traffic and hwy miles will make a huge difference too. ....as well as speed as mentioned. I noticed that with the 4EAT in the '08. .....really needed an extra gear.

Anyhow, I've never been able to achieve the MPG ratings they advertise. Nothing to do with the car but more my own driving style. The '08 got a consistent 20MPG and a bit better with my wife driving or on longer trips.

It's funny, right now my wife is averaging 22 MPG in her new 2020 with mixed driving. I'm hoping that improves a lot more but not really expecting it. She does have a LoadWarrior basket on top which on the '08 dropped the mileage by about 1MPG from my estimates.
 

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Discussion Starter #4
How fast did you drive it at 70 miles distance? If you drive this vehicle with a lead foot, ie hard on gas and hard on brake, it's drinks the fuel. Driving at 70+ mph, keeps this engine revved up to 3000+ RPM so it's going to suck up fuel.

So how fast did you drive? how hard are you braking?

have you looked at the spark plugs, air filter? Are any of the brakes dragging? What about tire pressure? What kind of tires? Large/wide AT tires will hurt MPG. Roof rack? Extra weight in the back? have you tried even filling up the tank and then calculating miles vs gallons after the fill-up? Making your judgement based on fuel gauge is not accurate.

But yes, if you feather the peddle and drive lightly with little stops and start, you can get 300 miles to the tank.
as far as I know everything on the car is factory spec, no big tires or anything and there’s literally nothing in the car currently other than a car seat and I’ve been driving very gingerly because It was actually a drive picking up my baby boy. So it’s about the absolute lightest easiest driving it could ever see and I’m still seeing horrendous mileage.

I haven’t had the chance to do any calculations like that but it was empty when I filled it up and after 70 miles it’s at a half tank. I know there’s something mechanical affecting the gas mileage, I just don’t know what it could be. Plugs seem fine but I haven’t done any sort of test on them just visual and filter seems fine. Oil is full and clean. I’d assume the tire pressure is fine because when I’ve driven other AWD vehicles and the tires were off-pressure you could REALLY feel it, but I haven’t checked them yet.

This is quite literally a YMMV sort of thing.

Let's say the "300 miles per tank" equates to just about 20 MPG (assuming he didn't run it dry all the time). Hell, the fuel light in my wife's old '08 would come into almost exactly when there was just over two gallons left. Trip B on the odo was reset every fill up and I told her that 300 miles was about as far as she should push it which should have left about 20 extra miles wiggle room.

Personally, I would start keeping a log between fill ups. Get the real MPG numbers based on your driving style, etc. Make note if those miles were mostly in town, hwy and so on. Only then can you get a reliable gauge on what range you can expect.

I'd also do the stuff suggested bman with a tune up (if needed), checking tire pressures, etc. Just remember that city traffic and hwy miles will make a huge difference too. ....as well as speed as mentioned. I noticed that with the 4EAT in the '08. .....really needed an extra gear.

Anyhow, I've never been able to achieve the MPG ratings they advertise. Nothing to do with the car but more my own driving style. The '08 got a consistent 20MPG and a bit better with my wife driving or on longer trips.

It's funny, right now my wife is averaging 22 MPG in her new 2020 with mixed driving. I'm hoping that improves a lot more but not really expecting it. She does have a LoadWarrior basket on top which on the '08 dropped the mileage by about 1MPG from my estimates.
I’ll definitely be logging the miles further, I do on all of my vehicles, always reset my trip at fill ups for situations exactly like this lol. I mean I definitely wasn’t expecting the advertised 25mpg on it but at this rate with an extremely rough calculation I’d say I’m getting close to 13-15 and that’s straight highway no traffic. Pretty much all of my driving is that way. I have to drive 2 minutes if that to reach the highway. I definitely have some more stuff to check (hard to do with the newborn) but I figured it wouldn’t hurt to post here and see if anyone else had any similar issues they may have resolved.
 

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2014 2.5i Limited CVT
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As mentioned - your mileage may vary....

The MPG on the Foresters is pretty good considering what they are - a bit brick with another brick on top. Not really the greatest for slipping through the air unmolested.

And a lot will have to do with your driving style and your drive... I work from home (no commute, yay!) and so all of my driving is done for errands and appointments and trips to the doggy park or such.. I'm almost never on the highway or freeway and deal with lots of traffic lights and stop and start and all of that.

I usually get about 300 miles per tank - but usually fill up before the little light goes on. So I'm seeing low 20s at best. Rough calculations being what they are... When I DO get to go out on the highway or freeway, I can see 350 or 400 miles out of a tank - upping considerably. But then again, I live in the US Desert Southwest and so my AC is on 4 to 6 months of the year - that takes from MPG. So does the roof basket (like @Kean ) and so do the all terrain tires I've added, the skid plates and more. It all adds up to steal MPGs.

I've also seen a low 200 mile range out of a tank - and may be seeing 17 MPG at times. I also do a bit of stop and wait (with the AC running because it's 100+ degrees outside) and that also eats MPG.

Review your drive and how you make that drive. I know when I keep my revs lower (under 3K) and cruise more, I get better mileage.
 

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Discussion Starter #6
As mentioned - your mileage may vary....

The MPG on the Foresters is pretty good considering what they are - a bit brick with another brick on top. Not really the greatest for slipping through the air unmolested.

And a lot will have to do with your driving style and your drive... I work from home (no commute, yay!) and so all of my driving is done for errands and appointments and trips to the doggy park or such.. I'm almost never on the highway or freeway and deal with lots of traffic lights and stop and start and all of that.

I usually get about 300 miles per tank - but usually fill up before the little light goes on. So I'm seeing low 20s at best. Rough calculations being what they are... When I DO get to go out on the highway or freeway, I can see 350 or 400 miles out of a tank - upping considerably. But then again, I live in the US Desert Southwest and so my AC is on 4 to 6 months of the year - that takes from MPG. So does the roof basket (like @Kean ) and so do the all terrain tires I've added, the skid plates and more. It all adds up to steal MPGs.

I've also seen a low 200 mile range out of a tank - and may be seeing 17 MPG at times. I also do a bit of stop and wait (with the AC running because it's 100+ degrees outside) and that also eats MPG.

Review your drive and how you make that drive. I know when I keep my revs lower (under 3K) and cruise more, I get better mileage.
thank you for the advice! I’ve definitely been driving it very gingerly and even so I’m used to driving bigass 4x4 trucks and muscle cars rated for like 12mpg or less. And when I drive them I DRIVE them. My sole drive with this car was putting down the highway with my baby in the back seat and it currently feels like the forester is getting the same gas mileage as them 😂 and that’s in total factory dress as far as I know. I just don’t know how one guy could see 300 miles out of one tank (he actually told me 320) and here I am at an apparent 140 miles. And I’ve got no reason not to believe the guy, and I don’t smell or see any fuel leaks. It’s just got me scratching my head.
 

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Discussion Starter #7
This is quite literally a YMMV sort of thing.

Let's say the "300 miles per tank" equates to just about 20 MPG (assuming he didn't run it dry all the time). Hell, the fuel light in my wife's old '08 would come into almost exactly when there was just over two gallons left. Trip B on the odo was reset every fill up and I told her that 300 miles was about as far as she should push it which should have left about 20 extra miles wiggle room.

Personally, I would start keeping a log between fill ups. Get the real MPG numbers based on your driving style, etc. Make note if those miles were mostly in town, hwy and so on. Only then can you get a reliable gauge on what range you can expect.

I'd also do the stuff suggested bman with a tune up (if needed), checking tire pressures, etc. Just remember that city traffic and hwy miles will make a huge difference too. ....as well as speed as mentioned. I noticed that with the 4EAT in the '08. .....really needed an extra gear.

Anyhow, I've never been able to achieve the MPG ratings they advertise. Nothing to do with the car but more my own driving style. The '08 got a consistent 20MPG and a bit better with my wife driving or on longer trips.

It's funny, right now my wife is averaging 22 MPG in her new 2020 with mixed driving. I'm hoping that improves a lot more but not really expecting it. She does have a LoadWarrior basket on top which on the '08 dropped the mileage by about 1MPG from my estimates.
In my search for answers I also saw something about the ECU needing time to adjust? Is that a thing?? And would it lead to absolute trash MPG?
 

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In my search for answers I also saw something about the ECU needing time to adjust? Is that a thing?? And would it lead to absolute trash MPG?
Sure..... I don't know about your model year and the extent of "learning" your ECU does but newer vehicles are typically designed to adapt to your driving style.

Having said that, I doubt it would have a significant impact on the gas mileage but just to what extent an ECU will change it's "tune" to adapt is really dependent on each particular application. It's sort of similar to the SI features on later model Subarus. With the push of a button the user can change the programming to something more aggressive vs. efficient. An ECU that learns from the driver after several cycles might adjust shift points, etc. to accommodate the more demanding nature of their style. ....but again, a lot depends on how much the ECU is allowed to change, what exactly it changes and so on.

btw, I have had to reset the ECU in my wife's old '08 a few times and that car apparently had a learning feature. In fact, it was always difficult to start the first time after that. ....but I never noticed any kind of significant variance in mileage after a reset.
 

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Discussion Starter #9
Sure..... I don't know about your model year and the extent of "learning" your ECU does but newer vehicles are typically designed to adapt to your driving style driver.

Having said that, I doubt it would have a significant impact on the gas mileage but just to what extent an ECU will change it's "tune" to adapt is really dependent on each particular application. It's sort of similar to the SI features on later model Subarus. With the push of a button the user can change the programming to something more aggressive vs. efficient. An ECU that learns from the driver after several cycles might adjust shift points, etc. to accommodate the more demanding nature of their style. ....but again, a lot depends on how much the ECU is allowed to change, what exactly it changes and so on.

btw, I have had to reset the ECU in my wife's old '08 a few times and that car apparently had a learning feature. In fact, it was always difficult to start the first time after that. ....but I never noticed any kind of significant variance in mileage after a reset.
thanks for the information. Much appreciated. Ive honestly never heard of that feature until I saw it on a subie forum browsing for answers. I’ll definitely try to eliminate a few more minor factors in the mean time but we’ll see 🤞🏻In my mind, if there’s an actual issue causing poor gas mileage it can‘t be that serious its gotta be something along the lines of fuel delivery/air intake/exhaust. But I haven’t figured out what.

But that’s coming from someone who knows zip about Subaru’s. Just based off what I know from working on my other cars/bikes
 

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Yeah, I personally think the first step is to get a handle on what exactly your mileage is first and go from there as bman first suggested. ....if for anything to more accurately gauge the effect of any changes you make from here on out.
 

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1999 "L" - 231,000 mi. AT
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My miles per tank went from 400 to 300 and I was in a sweat. Original engine. Now it's back to 350+ and only difference is if I drive 65 or less and away from dense traffic. Urban commuting cars are always run in the worst mpg conditions, IMO. Suggest you compile gallons used over miles run for 3 tank fulls before getting too upset. Welcome!
 

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My 2001 gets 15-17 mpg in town, which is nearly all of its regular use, so I'm a little surprised at the "300-mile tank" expectation. A typical refill (seldom when the needle's on EMPTY) is 11-12 gallons. The best observed mileage was a weekend run from Pasadena to Santa Barbara and back, almost entirely freeway, and that worked out to not quite 28 mpg.

Aside from an old pickup truck I ran for a while, the Forester is the thirstiest car I've ever owned. OTOH, it is comfortable, lovely to drive, and has been a sweet, intensely useful and reliable tool. And it's working happily on its third hundred thousand miles
 

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Re: High-speed driving: I just now read an observation that running at 70 or so will kill your mileage. I should mention that my usual freeway speed is somewhere around that, and while its OTR mileage is not up to that of our other cars it is still a lot better than what it gets on just grocery runs. I will admit that the 27+ mpg trip I reported included a fair amount of 25-30 mph heavy weekend traffic.
 

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Your engine has to go into closed loop for the O2 sensor to regulate the fuel/air mixture for optimum mileage and low emissions. Using a scanner check the fuel status. See if the engine comes up to temperature-195F. If it does not the thermostat could be missing. Or the ECT sensor is defective and indicating the temperature is too low to go into closed loop.
 

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Hello all, new to Subaru’s but I’ve owned and maintained many vehicles. I recently purchased a 2003 Subaru Forester 2.5X as my beater daily for work. 100,000miles on the engine. The whole reason I bought it was because I needed something with decent space and decent MPG, and the previous owner (I know, can’t be trusted but still) claimed he got around 300 miles on a full tank. After driving it for a whopping 70 miles I’m now reading a half tank. I realize they’re AWD and don’t get amazing gas mileage, I’ve owned other AWD vehicles, but at this rate I know something has to be wrong. I don’t smell any fuel leaks, but I haven’t ruled that out either. Any help/recommendations regarding the situation or what could be wrong would be greatly appreciated. Overall the car runs great super smooth thats why I’m stumped. I’ve never seen a literal 50% decrease in gas mileage in anything I’ve owned.
I've owned 1999, 2003 and 2009 Foresters and they all got between 22 and 25 mpg and on secondary roads i'd get around 25 mpg and driving hard on the interstate 75-80 it drops to 22 or 21 mpg.
I've put miles on those vehicles at the rate of 90,000, 225,000 and the 2009 now has 389,800. Consistent mileage of 22-25.
 

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My 2001, get's 17-19 mpg in the city. That means trips of 5 miles or less. 1-2 miles or less between traffic lights. On the Highway, I have seen 23-25 mpg. However once I go past 65mph and approach 70, it plummets back down to 20 mpg.
 

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My 2006 (no turbo, no frills) is driven at highway speeds of around 65mph virtually all the time, and there's a significant amount of around town, where I seldom get left at the traffic lights. I generally get 560 to 580kms on a tankful, but that's a tankful run right down to dry. When I do trips and run only highway mileage (plus some intermediate towns) I have had up to 660kms from a tank on one car, 720 on the other (yes, I have two the same)

But reliability of the fuel gauge on the second is a big issue. At times it shows half full after 120kms... just like yours. But at other times it's nearer to accurate.

560kms is 348 miles. I've seen worse than this when I've flogged it, using 80mph on back roads and the like, and also when a plug lead was out.

Load, for the sake of everyone who thinks otherwise, makes so little difference to things it's not worth considering. Put half a ton in the car, as long as the tyres are pumped up as they should be, and it will go just as far in highway running as it will with only the driver.

I've found 70-90kms is the normal distance that can be travelled after the fuel warning light comes on. Or 15kms after a bit of starvation on a tight left hand bend.
 

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Have you done the math?

I'm always leery about people who claim crappy mileage but never do the math. Fill the tank, set the trip odometer to zero and then drive 'til almost empty. Fill the tank and divide the gallons pumped into the mileage on the trip odometer. If you have a faulty fuel gauge or sender your pie in the sky mpg guesstimate goes right out the window. So you may be getting all worked up for nothing. Do the math.

BTW, the Forester is well known as not a champion when it comes to fuel mileage.
 

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2006 Forester 5-speed manual
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That's always the case. I even know people who guess their mpg without filling the tank right up!

If it's an automatic you can expect lower mileage, of course. Mine are manuals.
 
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