need help with Subby impreza 2010 MPG

[Dr. Jerryrigger]

I have a 99 with a 2.2L, and a AT. I've never gotten better than 28.5mpg, and in heavy city traffic I often get under 20.
From what i've heard the AWD switch doesn't help. It also uses electricity from the alternator when you have it turned off.
The transitions are geared rather low imo. So your ideal speed may be 45 rather than 55. Drive gently, with the AT I almost never go above 2,000rpm, but that depends on traffic; safety first. I have the added motivation to do that because of an oil leak that drips on my exhaust manifold when I drive over 2K rpm.
Try to maximize DFCO mode. With a ScanGauge type tool it should be easy to get a feel for it. If you learn the point that DFCO turns off and down shift just before you can save some gas. I've found that my car doesn't go into DFCO mode at all under 35, unless I downshift. I've tried some P/N but not for a full tank so I never got a good idea if it was helping, but it didn't seem to be. Also, sometimes my brakes stop working when the car isn't running , so I don't do that anymore, except when pulling into a parking space (with my hand on the e-brake)
It's simple to take the A/C belt off of these motors, and I gained just shy of 1mpg doing so. (my A/C didn't work, so I took the compressor out too) you might want to do that in the fall, rather than now, depending on where you live.
Then there are the things that work for all cars, many of which have been listed by others, but I will too:
tire pressure
Thin synthetic oil, trany fluid, front and rear gear box oil (I really need to do that one, it's been 40K miles...
New plugs and wire, if needed (not a big deal, that coil pack has some pep)
take off roof rack
Use the AC sparingly if at all
don't open your windows more than 1 to 2" at highway speeds
Block your radiator, or grill in the winter when your using heat
If you have any long lights on your commute turn your engine off when you know you'll be going no where for a few min. (might not be legal)
Accelerate and decelerate very gently
If you see my grandmother passing you your doing it right
Injector cleaner now and then may be good.
Good luck, Hope this helped

[Gribble1986]

Hi,
I thought I would just add about a trip I just did with my sister and mom. We just drove from Colorado Sprngs, CO to Grand Rapids, MI with her 09 impreza loaded to the gills! I had stuff almost falling on me in the back seat (moving).
Here is the stats for the trip:
22,000k on car with original air filter.
1200 miles for the trip, over 800 miles at 76-79mph
Used AC the entire time, sometimes on the second setting.
We averaged 31.7mpg.
Used 91 unleaded.
I'm really not sure how we did so good with our mpg average because I was the only one trying to save gas, they just wanted to get home.

In the Springs my sister would drive 15 miles round trip to work half highway, half city and would average 26mpg on 91 unleaded because of the high altitude and 85 or 89 wasn't running good.

[Dr. Jerryrigger]

It seems odd to me that you seem to need the higher octane. I know very little of newer subies, but like most new ICE cars they have a knock, MAP and O2 sensor, it seems like the computer should adjust for the altitude with out any problem. Have you compared MPG of different fuels? The placebo effect can be rather profound with car stuff (maybe have a friend fill it with an unknown grade to test). Do they recommend higher octane than "regular' in the manual?

Subaru keeps changing things for the worse. They don't even make the 2.2L engines any more, and they had too much power in my book. Now they switched the 3.0L H6 for a 3.6L H6, who needs that, a old 1.8 is enough for even a forester! When it comes time I don't think I'll get another subie (i'm on #2), unless I find a really old one with out much rust (not so easy in New England).

[brucey]

When I drove through Colorado last year in mine, I ran 85 octane in it as I went above 5000 feet. I've never been above 5000 feet before that, but the car had 0 power. I am talking like 2nd gear to stay moving on the interstate. The next tank I put the highest grade in it I could, and it was much better. Still down on power, but I could get by with 3/4 depending on the steepness.

[Gribble1986]

It wasn't so much the MPG on different grades of gas but more so like what Brucey said the lack of power and it a knocking noise at different times. In Colorado they only offered 85, the mid grade I think was 87 but maybe 89, and high was 91.
I also couldn't believe that 91 in CO was the same price as regular is in MI $2.75gal about.

Either way on grade of gasoline, having at lest 800lbs or more in the car running 76-79mph with AC on and still getting almost 32mpg seemed pretty good to me.

[hackish]

One thing that helps all subarus on the fuel economy thing is an aftermarket exhaust system. It's tough to get one that isn't obnoxiously loud. I recorded almost 15% improvement on my 2.5RS (about 10 years ago) by installing headers and a complete exhaust system. From the factory they are very restrictive.

-Michael

[Zerohour]

+1 with Hackish comment

I have a 2001 Outback sedan, factory exhaust is a power kill. Not sure how well the new ones do, but I can tell you the 00-04 Outback/Legacy had a terrible exhaust. Quiet, but HP restricting. And it sounds dumb to say when you'er trying to conserve gasoline, but having the AWD parasite loss, extra power allows you to stay in top gear longer/entirely for hills.

[hackish]

A few things to keep in mind when criticizing factory exhaust systems... They design the things to be really quiet so they satisfy all types of potential buyers.

They also have to pass emissions in a lot of different countries. A more restrictive exhaust can often light off the cat much quicker. Cold cats don't do anything for your emissions! Some countries have more restrictive cold start requirements so the vehicle can pass without the company having to redesign their exhaust system for each market.

I really wanted to design some exhaust systems for fuel economy but it turns out it's really hard and really expensive to leave emissions unchanged. Sometimes just 50 degrees of cat difference can have a 200% effect on emissions output.

[autoteach]

subaru only egr's the driver side rear cylinder. I really dont know how much this matters, but I imagine that it can't help much. as for exhaust restriction, you can de-restrict if post cat and see what the effect is.

AWD- that car is spinning all the drivetrain all the time. When you pull the fuse, you are only deactivating the center differential. All this does is take away input torque to the rear, you are still dragging the rear drivetrain down the road.

To maximize your efficiency, try to see if the drivetrain has the half shafts at level when the car is sitting on the ground. If not, lower or raise the car to do so. This will increase the efficiency of the drivetrain.

Just some ideas.