Why does my mileage suck?

[DubMutant]

2001 Outback LL.Bean Ed. H6 3.0L

 

Now besides the obvious engine factor on mileage, I cant seem to get more than 22-23 mpg on the highway- 2 times tested same result. I tested at 65-75 mph and got the same crappy mileage.

I am using hi-test 93 octane gas.

The oil is fresh.

The car recently had a 45,000 mile factory service.

 

What can I do?

I have heard that changing over to all synthetic fliduds can gain a few miles per gallon.

Is the EPA mileage rating that off? It states the car gets 27 mpg highway, 20 mpg city.

 

Can I change the valve timing via software for different driving conditions? I have searched and there does not seem to be any such software for this engine.

Plenty of stuff for STi and WRX but nada for the Outback I have.

Any suggestions?

[brus brother]

I have a 200 Legacy GT 2.5 4 cyl auto and that's about the same mileage I get. I can use 87 octane in mine most times of the year (a little knock in summertime). If your's is a manual trany you could expect better mileage. I've read that a failing front O2 sensor can worsen performance.

[porcupine73]

Hi as far as I know only the turbo ECUs support access ports such as Cobb.

 

Maybe give engine a good seafoaming, make sure brakes aren't sticking etc.

 

If you live in an area that switches to winter blend gasoline that will make mileage worse. Especially if the two tests you did were recent; I think most areas switch to winter gas around early/mid november. Ethanol reduced mileage too.

 

Actually that is not really too bad a mileage for the H6 at those speeds 65-75 mph.

 

I believe the H6 has two front o2 sensors. H6 came only with auto trans.

[Distance Commuter]

2001 Outback LL.Bean Ed. H6 3.0L

...I cant seem to get more than 22-23 mpg on the highway- 2 times tested same result. I tested at 65-75 mph and got the same crappy mileage... I am using hi-test 93 octane gas... The oil is fresh... The car recently had a 45,000 mile factory service.

 

What can I do?...

Any suggestions?

 

Increase tire pressure.

It's a standard technique among high-fuel-economy folks.

We usually put our tires at least at the max sidewall rating; some of us go higher than that. For 4wd Subies, maybe 5-10% higher in front vs. rear tires if that's what your oem spec's say.

 

Below is quoted from

http://www.carbibles.com/tyre_bible_pg2.html

 

For the first two years of our new life in America, I'd take our Subaru for its service, and it would come back with the tyres pumped up to 40psi. Each time, I'd check the door pillar sticker which informed me that they should be 32psi front and 28psi rear, and let the air out to get to those values. Eventually, seeing odd tyre wear and getting fed up of doing this, I asked one of the mechanics "why do you always over-inflate the tyres?" I got a very long and technical response which basically indicated that Subaru are one of the manufacturers who've never really adjusted their recommended tyre pressures in line with new technology. It seems that the numbers they put in their manuals and door stickers are a little out of date. I'm a bit of a skeptic so I researched this on the Internet in some of the Impreza forums and chat rooms and it turns out to be true. So I pumped up the tyres to 40psi front and rear, as the garage had been doing, and as my research indicated. The result, of course, is a much stiffer ride. But the odd tyre wear has gone, and my gas-mileage has changed from a meagre 15.7mpg (U.S) to a slightly more respectable 20.32 mpg (U.S). That's with mostly stop-start in-town driving. Compare that to the official quoted Subaru figures of 21mpg (city) and 27mpg (freeway) and you'll see that by changing the tyre pressures to not match the manual and door sticker, I've basically achieved their quoted figures.

 

So what does this prove? Well for one it proves that tyre pressure is absolutely linked to your car's economy. I can get an extra 50 miles between fill-ups now. It also proves that it's worth researching things if you think something is a little odd. It does also add weight to the above motto about not trusting forecourt pressure gauges. Imagine if you're underfilling your tyres because of a dodgy pressure gauge - not only is it dangerous, but it's costing you at the pump too.

 

Fuel economy message board - http://www.gassavers.org

[uniberp]

2001 Outback LL.Bean Ed. H6 3.0L

 

Now besides the obvious engine factor on mileage, I cant seem to get more than 22-23 mpg on the highway- 2 times tested same result. I tested at 65-75 mph and got the same crappy mileage.

I am using hi-test 93 octane gas.

The oil is fresh.

The car recently had a 45,000 mile factory service.

 

What can I do?

I have heard that changing over to all synthetic fliduds can gain a few miles per gallon.

Is the EPA mileage rating that off? It states the car gets 27 mpg highway, 20 mpg city.

 

Can I change the valve timing via software for different driving conditions? I have searched and there does not seem to be any such software for this engine.

Plenty of stuff for STi and WRX but nada for the Outback I have.

Any suggestions?

 

Drive like you have an egg between your foot and the throttle.

[Reveeen]

Because each and every car is a bit different you have to play with it.

I get my maximum mileage on the highway @58mph (2400rpm), anything more, and my MAP sensor "sees" boost, and dumps in extra fuel. The difference (in my case) between 58mph and 65mph is 6mpg. I *guess I'm trying to say: in high gear drive with your tachometer, not your speedometer, to get mileage.

[CNY_Dave]

Similar results here in Central NY.

 

I think I just missed getting to some real mileage testing before they switched over to winter-blend (I'm guessing. Got the car in Oct.).

 

I know in CT a few years back they switched over to 10% ethanol, if they did that in mass that will be a mileage hit.

 

I heard 10%ethanol (gasohol) is not always labeled as such. There are quick&easy ways (google for it) to check if it has ethanol in the gas.

 

I managed to hit 23.7 or 23.8 at my best, on mostly highway.

 

Dave

[nipper]

10% gasahol isnt going to do a thing, especially in NY, as its been here since the 1980's. So thats not a valid reason.

 

Your supposed to get 20/27, so 23 is a little low.

 

Now that 23 is at the old test method of 55 mph. Thats note #1. #2 is tire pressure and brand make a differnce. The higher mileage rated tire, the harder the rubber, the less rolling resistance.

 

Your right foot is huge reason for gas mileage, you may need to retrain it. A scantool or a mechanical vac gauge will help with that.

 

We have also changed to winter blend fuel (nov 1) and if you have had cold weather, your mielage will be lower.

 

nipper

[Towel Rail]

We usually put our tires at least at the max sidewall rating; some of us go higher than that. For 4wd Subies, maybe 5-10% higher in front vs. rear tires if that's what your oem spec's say.

 

A far safer plan would be to simply use narrower tires. That reduces the rolling resistance and unsprung weight without having to do stupid things like inflating the tires over the MAX sidewall rating.

 

My recommendations for overall economy are to lose weight (passenger(s) and cargo), keep the car in tune, and drive slower.

[daehttub2000]

Lots of good suggestions here. You might want to take down your Red Sox flags and take out all the baseball junk in your trunk:lol:

 

But seriously, if you have a roof rack system and a lot of extra gear in the back, it will affect your mileage. I'm always amazed at what accumulates in all the little storage compartments and under the seats in my old wagon. Depending on your roof rack configuration and what you carry, a fairing might help. It would allow you to put more BoSox stickers on your car which are more aerodynamic that those car flags:grin:

[nipper]

A few more thoughts:

Lazy Thermostat

Lazy O2 sensor

bad knock sensor

lazy Engine temp sensor

 

 

nipper

[mikem]

I have an 05 H3.0 Outback wagon. Last week I drove it about six hundred miles on vacation. First thirty or so were rural roads, then about 100 miles of interstate at 65mph, then 100 miles of interstate at 70mph. Averaged 28mph with the tires set to factory specs, 32 front, 30 rear. The tires are Michelin Hydroedge with a tread wear of 800. I then drove on the sandy beaches of the Outer banks for about twenty miles then repeated outbound trip on the way home. Overall mileage was 24.5 all on 87 octane winterized fuel.

I think the two most important factors in mileage are brain and foot.

[nipper]

Last week I drove it about six hundred miles on vacation. Averaged 28mph with the tires set to factory specs, 32 front, 30 rear..

 

i am SO not driving behind you

 

:-p

 

nipper

[thatswhatshesaid]

I've noticed similar MPG numbers in my H4 '00 Outback. I think the biggest problem must be the right foot. I can squeeze out 2MPG more per tank if I go easy on the long and skinny pedal. These big, heavy cars take a lot of juice to accelerate. Take it easy on the go-pedal and the motor can ease into cruising speed without going all the way to redline before shofting. When you boot it at the green light, she'll spin way up into the 5 mile-per-gallon RPM range. But you already knew that.

 

Here's another thought:

Go easy on the short, fat pedal, too. The friendlier you are to the brakes, the more likely it is you'll be nice to the throttle, too. I try to make stop-and-go traffic more like slow-down-and-go traffic. The huge slash in fuel economy comes from moving the big, lumbering beast from a stop. So...try not to stop. I see huge fuel economy increases when I look very carefully at every stop light, figuring out which lane to get in to be ahead of the pack and watch the adjacent lights to hit the green precisely when it switches, so I only have to slow down, not stop...

 

 

Oh, and kick all your kids and car-poolers out!

[mikem]

i am SO not driving behind you

 

:-p

Thanks for the spell check. No wonder I didn't get to spend much time at the coast!!!

Must have been 28mpg.

[CNY_Dave]

10% gasahol isnt going to do a thing, especially in NY, as its been here since the 1980's. So thats not a valid reason.

 

Your supposed to get 20/27, so 23 is a little low.

 

Now that 23 is at the old test method of 55 mph. Thats note #1. #2 is tire pressure and brand make a differnce. The higher mileage rated tire, the harder the rubber, the less rolling resistance.

 

Your right foot is huge reason for gas mileage, you may need to retrain it. A scantool or a mechanical vac gauge will help with that.

 

We have also changed to winter blend fuel (nov 1) and if you have had cold weather, your mielage will be lower.

 

nipper

 

 

Gasohol down near NYC, eh? Bummer.

 

Still have the real thing up here- for now. If they switch, my XR650L will be spitten and farten and I'll be swearin'!

 

Ethanol contains less energy per volume than gasoline, so the effect might be slight, but gas mileage will go down a skosh. The effect is much worse though on non-closed-loop engines, like older cars and motorcycles.

 

Dave

[srs_49]

I seem to get a little better than what you reported with our '02 H6 OBW, but not by a lot. We get 23-24 mpg going to the mountains, usually around 75 mph with a Thule luggage carrier on top (which can't be helping gas mileage). Don't think I've ever seen anything over 25 mpg. Usually run mid-grade (89 octane).

[DubMutant]

Guys- great discussion here.

 

I will re-check the tire pressure, as the temps have dropped signifigantly recently maybe too has the tire pressure- cooler air =lower pressure. Ive heard of guys re-inflating their tires with "winter air". I don't know the truth in that...

 

I am a very light pedal guy. My other car, a '84 Mercedes 300D is a heavy car with a lot of torque, so using the transmission in it's low torque band and not revving the ish out of it is always better in the long run, I especially keep her rolling most times I can. Unless Im getting on the highway I have a light pedal foot...I also find that the BioDiesel I use will sometimes decreases the power, so I need more pedal, but thats a different message board.

 

I hate ethanol. Period. It is a huge waste of resources. and the energy return is negligible. If I could find non-ethanol gas I would use it.

 

I found that the stealership had delivered the car to me 1 quart low on engine oil. (thanks guys) After topping off, my mpg's have increased- the significance has yet to be determined.

So, low engine oil=low mpg's

 

All runs performed with an empty car. I keep really clean crs. In fact, I sometimes remove the 65 lb back seat in my 96 2.0L Jetta with 240K, to get better mpg, usually I increase it 1-2 mpg's, she still runs 32-33 mpg's. I use Valvoline SynPower 10w-40 in this car. I plan to switch to that in the Suby.

 

I still want to run software thru the ECU so I need to find out if Cobb can do that.

 

No comments on the switching to all synthetic fliuds...any thoughts?

Happy Black Friday everyone!!! shop till ya drop.

[nipper]

Ethanol isnt done for the energy return, its done for emissions. Its much better and safer then the oxyginated fuel.

 

I dont understand all the noise about gasahole (10/90) mix, as its been around since the 1980's in some parts of the country. Its really harmless.

 

Its the e-85 thats a huge waste of resources.

 

nipper

[DubMutant]

Ethanol isnt done for the energy return, its done for emissions. Its much better and safer then the oxyginated fuel.

 

I dont understand all the noise about gasahole (10/90) mix, as its been around since the 1980's in some parts of the country. Its really harmless.

 

Its the e-85 thats a huge waste of resources.

 

nipper

 

 

huh. I learn something new everyday.

thanks nipper.

B-