Maintenance items to check for fuel economy?

"NaturallyAspirated" (NaturallyAspirated) 08/09/2013 at 12:51 • Filed to: None

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I've been tracking the fuel economy on my '98 Subaru Legacy Outback with Fuelly: !!!error: Indecipherable SUB-paragraph formatting!!!

As far as I'm concerned, ~23MPG in a 15 year old AWD station wagon with 215,000 miles on it is pretty darn good. The issue is that I've started to drive longer distances a couple of times per week (60 mile round trip twice a week for martial arts practice for instance), and the weekly $40 fill ups are starting to get to me - they used to be every other week.

Short of buying a new car, which isn't an option for me at present, are there any maintenance items that I should check that have an effect on fuel economy?

Here's a list of things I've done to the car already:

All fluids changed (oil, coolant, brake fluid, P/S fluid, transmission fluid, rear diff)

New front O2 sensor

Headgaskets (this made a huge improvement in fuel economy - duh)

Valve lash adjusted when headgaskets were done

Both front CV axles replaced

Replaced damaged / cracked exhaust components (new center pipe, new gaskets)

New timing belt, pulleys and tensioner

New air filter

New tires, maintained with proper air pressure and regular rotation

Professional alignment

Sweet amateur radio callsign license plates

Edit: I guess I should list the car's specs too, shouldn't I? It's a 1998 Subaru Legacy Outback with the Phase I 2.5L DOHC engine and 5-speed manual gearbox.

HammerheadFistpunch > NaturallyAspirated 08/09/2013 at 12:58

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There isn't much left to do as far as mileage, sounds like it should be running pretty well though.

GreenN_Gold > NaturallyAspirated 08/09/2013 at 13:26

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Fuel filter?

Inflame333 > NaturallyAspirated 08/09/2013 at 13:29

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Yeah, pretty much the best it's going to do.

The AWD is killing you.

I had a 95 civic dx 5 speed that averaged 34-35mpg, twas a good car.

NaturallyAspirated > GreenN_Gold 08/09/2013 at 13:31

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But a clean fuel filter will just allow MORE fuel to get to the engine and REDUCE fuel economy, right?

Right?

Yeah I should probably change the fuel filter.

dinobot666 > NaturallyAspirated 08/09/2013 at 13:37

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There is not much you can do to improve the fuel economy of a slightly heavy, AWD wagon, with a 4 speed automatic coupled to 4.44 gears.

NaturallyAspirated > dinobot666 08/09/2013 at 13:51

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It's a 5-speed stick, but yeah, I agree with your assesment.

Takuro Spirit > NaturallyAspirated 08/09/2013 at 13:53

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Manual swap it, and put on bigger tires.

I was constantly seeing 30+ MPG in my beast, and that's with the lower 5th gear from an earlier Outback, and big stupid off road tires, and NOT driving it like a little old lady.

NaturallyAspirated > Takuro Spirit 08/09/2013 at 14:09

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It is a manual. I don't know what size tires I have, but they are the OE size and seem pretty chunky to me.

And I've never been accused of driving like an old lady :D. Boxer rumble > economy.

That's interesting that you got so much better mileage than I do. Did you have the 2.2l or the 2.5l engine?

dinobot666 > NaturallyAspirated 08/09/2013 at 14:14

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Outbacks with a manual are quite rare, but still get abysmal fuel economy.

dinobot666 > NaturallyAspirated 08/09/2013 at 14:23

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Also, while you're doing all this maintenance on the car, be sure to check the little plastic guard at the U on the filler neck. The guard traps leaves and mud and other gunk in there and can stay moist the whole time, eventually rotting out the filler neck.

Clean out the debris, then spray a few coats of undercoating or corrosion resistant paint on the neck. Otherwise you'll be replacing the whole neck some day. Ah, the joys of Subaru ownership. :D

Takuro Spirit > NaturallyAspirated 08/09/2013 at 14:49

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Oh boy, it was a mish-mash of a car, but the mileage was always around 28-30 on the highway, with about 15% city driving mixed in.

It went from a 4-door 2.5GT manual, then became a L wagon with a dead 2.2 and an autotragic, then it got the 2.5 out of the GT, then that died of head gasket confagaration, so it got a JDM 2.5 that hated our gas and would knock under quick throttle application when hot but I ran it on 87 anyways because FUCK that. It was lowered for awhile, it ran 14" winter tires for a bit, then it got lifted on Outback struts with 16" Fozzie wheels.

Then the trans started howling so I sourced a low mile example from a '95 with the shorter 5th gear for even HIGHER RPM on the freeways. Still managed to get around 30 in the warmer months, but in the winter I was glad to see 24-25.

Sold her off with 220k on the clock (70k on the motor, and 50k on the trans) and I hear she's still running around town, and rumbling blasting down the freeways.

Maybe the borla header, high flow cat, and 2.25" piping going into an STi muffler helped? Not sure, because it ALWAYS got the same mileage from stock to slightly modded.

Pearson Hurst > NaturallyAspirated 08/09/2013 at 14:50

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You're doing a damn sight better than my '97, auto, 2.5. I work 3 miles from home, so I never get it on the highway, and only drive it during rush hour stop and go shit traffic. I average about 17 MPG.

Union of Smog Techs of CA > NaturallyAspirated 08/09/2013 at 19:42

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Really though, I think you covered everything but I would like to know compression readings. Wait, PCV valve? And does rap cap pressurize system, that one drives me crazy, seen engines replaced but cooling pressure not correct after!

And never go past 3/4 throttle or ECM tosses fuel strategy out temporarily.

Outzen > NaturallyAspirated 08/10/2013 at 04:52

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Seems like you already have done what needs to be done. Next step might be weight savings, such as spare time removal and such. Or aero, lower it for better cd-value.

NaturallyAspirated > Outzen 08/10/2013 at 17:17

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I was thinking about the lowering. I've heard of folks importing the GT-B suspension from overseas, which would drop the car about 2". My only concern would be that I might have to put smaller tires on to clear, and I have less than 10k miles on my current set.