Increase my gas mileage!!!

BAC5.2 · Post by **BAC5.2** » Sat Mar 04, 2006 11:33 pm

The Forester is a pimp. I absolutely LOVE having it. Carries everything I need it too. Doesn't have any real issues that I can tell. I've done a lot of maintainence on it, and it's running pretty well overall.

But my gas mileage isn't really what I wish it was.

It only seems to get about 22 to 23mpg and I never really rag on it. It's, of course, a 5-speed, and I don't usually go over 3,000 RPM unless I am on the highway (70mph = 3000 RPM).

What kind of things can I do to increase gas mileage?

Cars.com says the est. economy is 21mpg city, 23mpg highway.

I would imagine that the 4.44:1 final drive plays a great role in the poor fuel economy.

Though my mileage is average (since I drive about 50% city and 50% highway), I still want more!

How are some of you guys getting 27 and 30 miles to the gallon?

I'm used to sub 17mpg in the Legacy, and beyond 45mpg on the bike. I'd like 25 or so in the Forester if possible.

Would things like an exhaust REALLY help fuel economy, or would it just be wasting money and increasing NVH? With the Forester, NVH is something I am opposed too.

vrg3 · Post by **vrg3** » Sun Mar 05, 2006 3:26 am

It's plausible that a suitable exhaust could improve fuel economy.

Some other ideas:

Underdrive or lightened pulleys
Lightened flywheel
Lighter wheels
Lower friction tires
MSD DIS-2
K&N air filter

I don't know how cost-effective these ideas are, though.

You should also try playing with tire pressure some; it does impact fuel economy noticeably.

I'd assume you're already running good synthetic lubricants in the crankcase, gearbox, and rear differential.

AWD_addict · Post by **AWD_addict** » Sun Mar 05, 2006 4:30 am

I recently got about 28 mpg going 70-78 mph. Using cruise control and driving like a grandma off highway seems to help the most. I'm using a K&N air filter too.

206er · Post by **206er** » Sun Mar 05, 2006 4:32 am

cut a little block of 2x4 and glue it to the back of your gas pedal.

evolutionmovement · Post by **evolutionmovement** » Sun Mar 05, 2006 6:47 am

The Forester doesn't have the aerodynamics of the Legacy. I think you're mostly stuck unless you want to strip it, but even then, drag is drag. It's a fairly jacked up car with a high frontal area and what's got to be awful drag for shape. Higher gearing would probably be the biggest thing you can do since I don't think you'll get as much as you want out of minor mods. Putting more air in the tires is free, though. I do that whenever I drive long distances and it's not a drastic difference, but it does help.

scottzg · Post by **scottzg** » Sun Mar 05, 2006 4:18 pm

thinner oils make a fair difference, as do hard thin tires. Lowering the forester may actually help. I've heard hooking a wideband 02 sensor and running it through a narrowband translator can help, but isn't cost effective unless you simply want to own the equipment.

fwiw, i got 22mpg on a tank driving 85-90 and 3 days later got 31 doing 70-75.

rallysam · Post by **rallysam** » Sun Mar 05, 2006 6:24 pm

Don't have any ideas, Phil, but FYI my RS 5MT (which has a lot of similarities) gets about 27 in mostly highway driving, and I'm not driving like grandma..

BAC5.2 · Post by **BAC5.2** » Mon Mar 06, 2006 4:10 pm

I've got a K&N somewhere in my garage, and I've got pretty good fluid in the tranny and the rear diff. I run 10W30 in the crankcase (too old for synthetic, I'll switch if I reseal the engine. I don't want to deal with any potential leaks).

I think it's probably just due to the brick-like aerodynamics and the high-ish ground clearance. Maybe I'll build an undertray for the whole car this summer.

I guess I'll have to be happy that I'm at least getting above 20mpg!

evolutionmovement · Post by **evolutionmovement** » Mon Mar 06, 2006 7:21 pm

An undertray will help a little. IIRC undercarriage and engine compartment drag is about 15% of the total.

LaureltheQueen · Post by **LaureltheQueen** » Mon Mar 06, 2006 8:41 pm

interesting. I may have a use for the old yield sign I picked up afterall!

evolutionmovement · Post by **evolutionmovement** » Mon Mar 06, 2006 9:51 pm

And <15% of 12 is still not even 14 mpg

Post by **DLC** » Mon Mar 06, 2006 10:39 pm

I was getting closer to 25MPG before winter, but it dropped to 22-23 when it began to get cold. It could have been coincidence that i got a CEL/MIL, but it cleared without returning.

I do need to switch back to Mobil 1 and get my lifters adjusted, it's been a year since I had the cams installed

J-MoNeY · Post by **J-MoNeY** » Mon Mar 06, 2006 11:20 pm

Toss 4oz of Acetone in there. That'll help. Maybe.

Bheinen74 · Post by **Bheinen74** » Tue Mar 07, 2006 6:06 am

the weight of an underbody tray, would not give you any benefit. You would have to strip parts off to make up for that weight gain, to get an aerodynamic gas mileage effect.
take out the radio, speakers, carpet, etc to lighten the chassis up. Get a set of Billet wheels, they are super light. Remove your spare tire......etc, if you get a flat your screwed. Take off the wiper arms, etc etc, this is a lost cause at this point. sorry i am of no help.
did you think about just doing a tuneup?

206er · Post by **206er** » Tue Mar 07, 2006 6:50 am

J-MoNeY wrote:Toss 4oz of Acetone in there. That'll help. Maybe.

I have been trying this for 4 tankfulls now, and have not seen an improvement. I am going to try 10 tanks and if nothing, I will stop. a lot of people have seen some pretty impressive gains from acetone though. the recipe to use is 2 oz per 10 gallons.

LaureltheQueen · Post by **LaureltheQueen** » Tue Mar 07, 2006 8:28 am

evolutionmovement wrote:And <15% of 12 is still not even 14 mpg

I'm going to kill myself

BAC5.2 · Post by **BAC5.2** » Tue Mar 07, 2006 5:39 pm

Bheinen74 wrote:the weight of an underbody tray, would not give you any benefit. You would have to strip parts off to make up for that weight gain, to get an aerodynamic gas mileage effect.
take out the radio, speakers, carpet, etc to lighten the chassis up. Get a set of Billet wheels, they are super light. Remove your spare tire......etc, if you get a flat your screwed. Take off the wiper arms, etc etc, this is a lost cause at this point. sorry i am of no help.
did you think about just doing a tuneup?

Car is in well enough tune. New timing belt, new coil pack, plugs, wires, oil changed religiously.

I wouldn't imagine a sheet-aluminum under-tray would be TOO heavy.

The car is something like 3400lbs, losing weight isn't much an option.

I guess it's about as good as it gets

scottzg · Post by **scottzg** » Tue Mar 07, 2006 10:51 pm

ej18 swap

dzx · Post by **dzx** » Wed Mar 08, 2006 12:38 am

start drafting other drivers

AWD_addict · Post by **AWD_addict** » Wed Mar 08, 2006 1:31 am

Pickups do that all the time, and they get poor mileage.

wiscon_mark · Post by **wiscon_mark** » Wed Mar 08, 2006 2:37 am

the 4.44 is definitely killing your mileage. If I could cruise at 2200 instead of 3000 on the highway (and this is with a 3.9!) my mileage would be much improved!

As far as intake efficiency goes, the air filter only makes up 1% of the restriction. The inefficiencies in the snorkus and the airbox (pressure drops due to pockets of trapped air and such).

So maybe getting a GOOD CAI (the cheapo ebay intake piping is supposed to help reduce turbulence a lot, according to dyno testing) and possibly ditching the airbox junk, as well as getting mandrel bent 2.25" Stainless Exhaust, might give you a bit more.

Maybe swap a 3.9 tranny in?

BAC5.2 · Post by **BAC5.2** » Wed Mar 08, 2006 3:59 am

I could probably do a 3.9 swap. I could easily get a ring and a pinion shaft that would probably work, and I have a 3.9 open LSD that I could use.

What kind of mileage do you get Mark? I'd only be concerned about the horrendous lack of pickup that the car would have.

I think I figured out why my gas mileage has been kinda down. My CEL came on on the way home today. Not much effect on drivability, maybe a slight sluggish feel. I'm going to guess it's a cat-inefficiency code or something like that.

I'll pull the snorkus. I don't want a huge increase in NVH with this car.

Maybe I'll dynomat the firewall and get headers and an intake. Just to see if I can free up gas mileage more than power. That'd be nice. Wouldn't be that much weight for the sparce amount of dynomat that would be used.

wiscon_mark · Post by **wiscon_mark** » Wed Mar 08, 2006 4:14 am

I get 26-29 mixed in the summer. Yeah, the car isn't exactly sprightly, but I doubt it makes that much difference, honestly. They're decently spaced for an N/A 2.2L

Snorkus only makes an NVH difference at WOT. And you don't do that much with this car, so I wouldn't worry about it.

Bheinen74 · Post by **Bheinen74** » Wed Mar 08, 2006 5:33 am

what kind of tire pressure are you running? newer tires?

you can get 2-4 mpg better with like an increase of psi for your tires.
If you run like 31psi now, go to up 35psi. make sure you check the max PSI pressure on your tires first, some tires are designed to safely hold more psi than other tires. It will change your ride and handling some. You may feel the vibrations if your wheels are not balanced, so you will probably want to get them balanced again.
Anything over 35 psi and you won't like the ride feel. anything under, you wont get as good mpg.

what is your timing setting? Is timing adjustable?
could increase it to point of where it wants to ping, then set back 1 degree. that will help mpg too.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Increase my gas mileage!!!

Increase my gas mileage!!!