Last post on Aug 18, 2008 at 6:25 PM
You are in the Subaru Legacy & Outback
What is this discussion about?
Subaru Legacy, Subaru Outback, Fuel Efficiency (MPG), Sedan, Wagon
#25 of 49 2007 2.5 base automatic, 34 mpg.
Jun 05, 2008 (4:47 pm)
This is my wife's car. She averages 21 mpg on day to day drive to work 7mile one way mixed city highway. I drove it from my work place 35 miles one way and got 34 mpg. I made a conscius effort to keep it in fourth gear at all times even at speeds below 40 mph.
Subarus are among the most fuel efficient AWD in the market. Much more fuel efficient than CRv's, RAV4, Rogue. The outback is even more silent and relaxed on the highway despite the short gearing. 2450 rpm at 60 mph seems steep but that is the most efficient rpm for a gas engine.
#26 of 49 Re: 2007 2.5 base automatic, 34 mpg. [peralta]
Jun 10, 2008 (7:13 am)
With a 7 mile commute one of the issues is that the engine isn't really operating at full temp for long, so she would do far better if her commute were longer.
It takes about 2 miles are so just for the engine to warm up and reach peak efficiency.
#27 of 49 Re: 2001 Outback Limited 2.5L H4 [paisan]
Jun 10, 2008 (6:46 pm)
I have the same 2001 with 120k miles. I just recently had the complete 120k service and have been overly faithful with the recommended services. I just recently got about 21/22 mpg in mixed city/backroad driving. NH does not really have big cities I usually run about 26/27 on with highway driving. Not too bad for a 7 year old car I would think.
#28 of 49 Re: Subaru Outback 2008 MPG [julecat]
Jun 18, 2008 (5:00 pm)
A lot will depend on your driving style. Certain weeks at a time I drive more... aggressively... both on the highway (NJ GSP/TP) and in the city (Newark, NJ). If I am in a rush and I'm tach'ing at 4.5k-5k RPMs when I shift, I will get noticably lower economy compared to, say, being gentle and shifting between 2.5k-3k RPMs.
Another big thing too is inertia. Objects in motion tend to stay in motion. Rather than accelerating into a red light, a prolonged brake which slows you from 50mph to say 20mph, then have it turn green and reaccelerating is better than 50mph to 0, waiting 10 seconds, then reaccelerating back again.
Another thing - highway speeds deteriorate due to parasitic drag (roofracks, too) which also includes the skin of the automobile (wash your car more often, wax it.) etc. This parasitic drag increases with speed exponentially - just like on an airplane (I'm a pilot, had to study this crap) - and you'll really notice beyond 55mph you start getting around a 10% loss in fuel every 10 mph you go - maybe more, if you have accessories like A/C running.
I noticed on a trip from NJ to FL, I had amazing mileage through NJ, MD, and DE where the speed limits are lower - 55 mph in some parts - compared to VA, SC, NC where the speed limits are 70. It made the difference between 450 miles per tank (11.9 gal tank on my Civic) and 350.
Keep in mind that your sticker rating on the side of your car is based on a highway speed test at 55mph for the highway rating. If you have a lead foot, like my wife, then you really may want to consciously try slowing it down - just 5 mph or 10 mph for a week - and see if there's a difference.
Typically, on my average commute of 10 miles, with an average speed limit of 55, it takes me about 20 minutes. Going 5mph faster would only get me there about a minute or two faster, but I don't feel like getting pulled over by the cops that wait in the bushes (they're in the same spot every day, haha!)
Ethanol does NOT have as much bang for the buck compared to gasoline, and by that, I mean energy measured in joules per given volume of liquid. In addition, lower octane fuel doesn't give as much energy per joule compared to plus or premium.
I'm not recommending you go and buy plus or premium unless you do some quick math to find if the extra mileage you're getting (say 50 more miles to a tank with premium, but you're spending an extra 10 bucks at the pump), is worth it.
So, if it's 25 cents more per gallon to run premium, and you get 15 gallons, thats 3.75 more for premium gas.
That's a little under what a gallon of regular goes for around these parts in NJ, so you'd have to figure you'd need to get at least 25ish miles per tank in order to justify paying the initial premium.
This takes a little investigation on your part, but you may want to look into it. I found by running Plus Test (91) in my tank, it costs me an extra 1.00 or so at the pump when I fill up, but I end up walking away with another 50 miles. That makes up for the extra gallon and a half of regular I'd need for my Civic - so I've started filling it with Plus.
I knew math would come in handy some day.
#29 of 49 Re: Subaru Outback 2008 MPG [pilot1226]
Jun 21, 2008 (2:25 am)
I just thought I'd also comment I don't condone everyone running out and buying premium fuel - the octane rating is simply the fuel's resistances to detonation (premature ignition). Higher-end cars that call for premium gasoline have a higher compression ratio in the combustion chamber (the specific ratio is typically found under the performance specs of the car), so the fuel needs to resist spontaneously combusting when it enters the chamber.
I would keep in mind too that you could - keyword COULD - run into fuel injector issues if you continuously run 93+ octane in a car that says "Unleaded 87 or better". I usually run plus test when I have long road trips, and a tank of premium every few months.
If you want more information on why not to run premium constantly in a car built for 87 octane, Google it. There's a lot of returns.
#30 of 49 Re: 2007 2.5 base automatic, 34 mpg. [peralta]
Jun 24, 2008 (6:54 am)
While we're all talking about MPG's, I figured I have a deep thought for us to discuss:
Gasoline is sold by volume (gallons in the USA). Temperature is directly proportional to density (If you have thing "x" at two temperatures, one higher and one lower, the lower temperature one is more dense.)
My thought is, if you purchase gasoline in the early morning hours before the sun rises and starts re-heating the earth, you're getting more gasoline than when you purchase it in the middle of the afternoon. While the volume is the same, the density is different, and in theory you should be able to get better mileage out of the tank that was filled in the early morning.
#31 of 49 Re: 2007 2.5 base automatic, 34 mpg. [pilot1226]
Jun 24, 2008 (6:59 am)
There was a news report on this recently, but I unfortunately don't remember the news source. The bottom line, however, is that whatever gain you get is really minimal and not worth the effort.
#32 of 49 Re: 2007 2.5 base automatic, 34 mpg. [pilot1226]
Jun 24, 2008 (1:06 pm)
The tanks are underground and well insulated from temperature fluctuations.
Jun 25, 2008 (11:29 am)
lower octane fuel doesn't give as much energy per joule compared to plus or premium.
isn't a joule a joule regardless of its anti knock capability????
#34 of 49 Re: joules [cptplt]
Jun 25, 2008 (5:18 pm)
Yes and no. Since there's more resistance to premature detonation, there's more power in the bonds of the hydrocarbon, therefore it releases more energy when the bonds are broken.
It's a minimal gain.