Official 2.5 mpg thread

[CaptEditor]

I have been a bit dissapointed with my mpg and I am curious as to what other 2.5 owners are getting.

 

 

Please specify as much as you can:

1. mpg averages for City, Highway, and/or a general mix of the two
   
2. Model and year
   
3. SOHC or DOHC, mileage of engine, turbo or non
   
4. Automatic or Manual Transmission
   
5. Fluids in engine, diffs, tranny, etc.
   
6. any Intake, Engine, or Exhaust Modifications
   
7. Tire size and type
   
8. Suspension lifts/lowering and/or aerodynamic changes (such as mirrors, roof racks, light bars, bumpers, valences, etc.)
   
9. Any other factors you feel are relevant
   

 

 

Let's avoid pictures unless it is to show aerodynamic modifications or hard items to describe.

Keep it on topic for other discussions use PM or a new thread!

Edited April 28, 2010 by CaptEditor

[CaptEditor]

I'll start us off!

 

1. City: 16-19

Highway: 19-23

Towing 90% Highway: 19-20

2. 2004 Outback Wagon

3. SOHC coming up on 60k miles

4. Automatic (4EAT)

5. Castrol Syntec 5w30, Redline 75W90 Synthetic Diff Oils, Mobile 1 Synthetic ATF

6. No modifications under the hood

7. 215/65R16 General Grabber AT2's

8. Newly Installed King Springs (hae not recorded MPG with them yet)

9. I have a stock LSD in the rear. I get gas at several different stations all of which contain up to 10% ethanol. I also have NGK single electrode iridium spark plugs, properly gapped, with original plug wires.

 

My towing mpg is barely effected because the trailer is aerodynamic and only 750lbs dry.

 

 

I am very curious what difference slimmer mirrors would make on my mileage. I love the large viewing area especially for towing, but they certainly drag a lot in the wind!

 

 

-Kevin

Edited April 28, 2010 by CaptEditor

[gbhrps]

I'll go next.

1. 34 mpg (Canadian gallons, about 5 US quarts make up 1 of our gallons) all day long on the highway at 100 kmph (60mph). (Note: its a flat as a postcard for 100 miles in any direction where I live) Never checked the city mileage.

2. 2007 OBW LTD

3. SOHC just hit 100 000 km (60 000 miles)

4. Automatic Sport Shift

5. Castrol GTX 5W30

6. Dead stock

7. Original Bridgestone 17 inchers (swapped winters with 16 inch Toyo Snows)

8. My third OBW LTD, but not my last.

[robm]

Actually, the conversion from Imperial to US liquid measure is 5/6, not 4/5.

 

3.785 liters to the US gallon.

4.546 liters to the Imperial gallon.

 

34 MPG (imp) is 28. 3 MPG (US).

[mr.radon]

1. HWY - 28.6 mpg - average speed, 68mph
   City - 24.5 (I try not to jack rabbit starts and roll through stop signs if it obvious there is not cross traffic. (stop signs that would be yields in any other country)
   
2. 1998 Outback
   
3. 225K, DOHC
   
4. Manual Transmission
   
5. Engine, Mobile 1 Fluids in engine, diff & tranny, royal purple Synchromax
   
6. No Intake, Engine, or Exhaust Modifications
   
7. 205/70R15, Goodyear Assurance (36psi)
   
8. Took off roof rack
    
   Recent head gasket, valve lap, seals... DOHC
   

No leaks, burn about a 1/2 quart of oil every 4K. (oil changes)

 

Needless to say I am SUPER happy with my ride after I rebuilt the engine.

[doc526]

Please specify as much as you can:

 

1. work week combo of city and hwy - 24-26mpg. (shift at 3000 rpms)

All hwy (drove from Atlanta to Orlando 2 weeks ago) - saw 29-30 mpg with AC on.

2. Outback Wagon - 1997

3. DOHC - approx 160K miles

4. Manual 5MT (4.11 diffs)

5. Castrol GTX 10-30 engine. unknown in diffs and tranny. (diff and tranny changed by owner before i bought it)

6. K&N filter in stock intake. stock exhaust.

7. 205/70/15 Goodyear Assurance Triple tread. ( psi set to placard standards)

8. Stock roof rack.

9. I try to keep the hwy revs to 3500rpm and under.

Edited April 28, 2010 by doc526

[CaptEditor]

Does anyone else have an innacurate speedometer? My speedometer seems to be about 7% faster than the sign I drive by every day which posts your speed. If I drive appx. 37.5 mph, the sign says I am going 35 mph. I have driven past other identical signs on other roads in my county and the signs seem to be accurate with each other. I am assuming that they are in fact accurate in recording speed.

 

I do understand that my tires are an oversize from stock, however they should only affect my speedo by 1.4%, and my speedo was innacurate with my original Bridgestone Potenzas. This would make sense if Subaru used the same speedometer as the Legacy and never adjusted it for the increased tire size. I have heard that this may be true for the 2000-2004 Outbacks

 

Please let me know if there are any flaws in my thinking or math!

I did use a tire calculator to help me find some numbers: http://www.miata.net/garage/tirecalc.html

 

My calculated mpg:

267/14 = 19

 

Adjusted odo reading by 1.4%

(267*1.014)/14 = 19.34

 

Adjusted odo reading by 7%

(267*1.07)/14 = 20.41

 

This could be a fairly significant factor in my calculated mpg being so low.

I would love to get a GPS and compare my odometer reading on a tank to the GPS recorded distance. Anyone have experience with the accuracy of the GPS units?

 

Am I digging too deep into this?

 

 

-Kevin

Edited April 28, 2010 by CaptEditor

[lomita]

I do understand that my tires are an oversize from stock

 

-Kevin

 

Next time you replace your tires, get the equivalent OEM tire size in the 16 inch rim, and watch your gas mileage come right back up.

 

The little problem is the ECU cannot compensate for the change in tire "over size" from the "factory original size".

 

This not only happens on Soobs, but on our Suki as well. We went from 14 inch rims to 15 inch rims with an over size tire, the mileage fell off immediately. Then we downsized the tire back to the OEM size but on the 15 inch rims and the gas mileage returned to the higher original efficiency.

[doc526]

My speedo is fairly accurate. It was a repaired / swapped out before I bought the soob. The odometer did not match carfax records but I knew that when I bought it. :-\

 

I used the GPS on my blackberry when I drove to Orlando to check my speedo and it was always within +/- 1 mph of what the gps read.

[Suzam]

Our 2001 Outback 2.5 gets 20 to 21 MPG Local and 26-28 MPG highway.

 

Our 1998 Outback 2.5 gets 18-20 local and 24-26 highway.

 

Our 1997 Legacy 2.2 gets 22-23 local and 29-31 highway

 

I get at least 2 MPG more than the wife in the same car at any given time. Driving habits make a big difference.

 

 

They are all automatics the 97 2.2 has synthetic trans and differential oil. All run reg engine oil.

Edited April 28, 2010 by Suzam

[idosubaru]

speedometers are often inaccurate, they typically read higher than you're actually going, that's fairly common.

 

Next time you replace your tires, get the equivalent OEM tire size in the 16 inch rim, and watch your gas mileage come right back up.

actually it doesn't work like that and has nothing to do with the ECU. it's a dynamic relationship, some cars get better gas mileage with larger wheels/tires.

 

the Subaru XT6 comes stock with dinky 14" wheels/tires. Install 16" Impreza wheels/tires and highway mileage will increase. The 6 cylinder has plenty of power to move those larger wheels/tires and see a benefit.

 

My castrated Legacy with EJ18 though in my sig - that thing gets horrible gas mileage with 16" wheels, the engine is too small pushing that heavy legacy behind and automatic. Smaller wheels and the mileage goes up significantly.

[hankosolder2]

You guys with the alternate tire sizes are correcting your odometer readings before calculating MPG, right? A tire size change which throws the speedo readings off will also cause your odometer mileage to be off by the same percentage which whack out your gas mileage calculations....

 

Of course, the tire rolling diameter will change gearing too which can have a positive or negative impact on your MPG.

Edited April 28, 2010 by hankosolder2
clarity

[CaptEditor]

You guys with the alternate tire sizes are correcting your odometer readings before calculating MPG, right? A tire size change which throws the speedo readings off will also cause your odometer mileage to be off by the same percentage which whack out your gas mileage calculations....

 

Of course, the tire rolling diameter will change gearing too which can have a positive or negative impact on your MPG.

 

My initial post stated unadjusted MPG.

 

Would it be correct to adjust my MPG this way:

speedo is 7% fast

so multiply my odometer trip reading by 1.07

then divide it by the gallons consumed

[hankosolder2]

I think you have it backwards. If the speedometer is reading high (due to tires) the odometer will also read high. So you are getting worse mileage than it appears you are getting.

 

I'd bet that you can find an online calculator where you enter your old tire size and your new tire size and it'll give you the percentage off (I wouldn't assume that all of the speedometer error is due to tire size.) You could also drive some measured miles and compare your odo reading, work out a correction factor, etc.

[OB99W]

[...]I'd bet that you can find an online calculator where you enter your old tire size and your new tire size and it'll give you the percentage off [...]

http://www.net-comber.com/tirecalc.html

[CaptEditor]

I was using this calculator: http://www.miata.net/garage/tirecalcold.html

 

Plus the estimation of my observed speed verses my recorded speed on a speed monitor sign to get my 7% figure.

 

Smaller tires should spin faster, recording more revolutions (or miles) over a set distance and a higher speed on the speedometer. This should require a reduction in the recorded odometer trip meter to match the actual miles driven.

 

Larger tires should spin slower, recording fewer revolutions (or miles) over a set distance and a lower speed on the speedometer. This should require an increase in the recorded odometer trip meter to match the actual miles driven.

 

So I think you are right, hankosolder2.

 

So the stock 2004 Legacy tire size is 205/55R16

and the stock 2004 Outback itire size is 225/60R16

This is a speedometer difference of 7%

 

My tires are 215/65R16, giving me a difference from the stock Legacy tires of 8.5%

My calculations show that this is approximately the difference I am noticing on my speedometer. 38mph * 0.915 = 34.77 mph

 

This is really bad new for me. My mileage is far worse than I thought.

 

266 miles / 14 gallons = 19 mpg

Adjusted to my 8.5% reduction in the odometer reading:

(266*0.915)/14 = 17.39 mpg!!

 

I will have to record my mileage over the next few weeks/months to get a new estimate.

 

:banghead:

Edited May 17, 2010 by Qman

[hankosolder2]

Sorry to be the bearer of bad news! Maybe you should just put some really small tires on, enjoy your "great MPG" and forget all about this conversation.

[CaptEditor]

Sorry to be the bearer of bad news! Maybe you should just put some really small tires on, enjoy your "great MPG" and forget all about this conversation.

 

haha, that would look so sily with the lift and wouldn't help me down the forest roads!

[variant13]

Prior to my beloved Forester's encounter with a drunk driver:

 

Please specify as much as you can:

1. 21.5mpg in town driving, and 17.9 - 31.0 on highway (17.9 was on a trip to SLC in a *75mph* headwind - 31 was on a stay in CO where it is comparatively flat). In general highway was 28.5 mpg
   
2. 2000 Forester
   
3. No clue how many cams, I assume SOHC, 163,000, non-turbo
   
4. Manual Transmission
   
5. Plain Castrol 10-30.
   
6. IIRC 205 70R 16 - or whatever stock was?
   
7. I tend to drive like a granny, even on I-80 I seldom hit 80mph, and unless I'm crawling over Elk Mountain, I use cruise control.
   

[2.5_IMP]

1. 26-27 mpg mixed.

2. 2002 Impreza Outback Sport.

3. SOHC, 116,000, N/A

4. Automatic

5. Valvoline 10W30 High Mileage synthetic blend, Subaru Gear oil in diffs,

Subaru ATF in tranny.

6. Rallitek spark plug wires.

7. Pirelli P-Zero 225/60/R16 on some older Advan T/C lightweight wheels.

8. Stock

9. None

[Bucky92]

1. 29mpg all city....32-36 mpg varied city/highway.

2. 08 Impreza 5 door

3. SOHC 50,000 miles

4. 5 spd

5. Castrol GTX or Dealer serviced

6. factory roof rack cross bars,and factory rock guard.

7.Stock but seriously due to be replaced

8.Driving style varied.

[GLCraig]

1. 18mpg City, 30mpg at 55mph, 25mpg at 65mph, 22mpg at 70mph, 19mpg we I'm having some fun.

2. 2009 Impreza STI

3. DOHC Turbo 28,500

4. 6-speed Manual, DCCD, Front LSD, Rear LSD

5. Mobil-1 or Castrol Syntec in the engine, OEM fluids in Transmission and Rear Diff

6. Stock

7. 245/40-18 Dunlop SP Sport 600 (OEM Tire) about 30% tread left.

[avox]

1. Mostly City, some highway 21mpg

Highway @ 70mph (without speedo correction) = 26mpg

2. 2004 2.5RS

3. SOHC, 113,000km (70215 miles), non-turbo

4. Manual Transmission

5. Castol Syntec 5W-30, Stock Rear Diff Fluid, Redline Lightweight Shockproof(i know this is wrong in every way, but I couldn't get rid of the 2nd/4th gear

grind using any oils except this one..haven't tried Extra-S yet, but switching to it soon) Tranny Fluid.

6. Took out silencer box, SPT Axleback

7. Kumho Ecsta SPT 225/45/17 on 17x7.5 Rota Torque's

8. H&R Springs, Koni Inserts in WRX struts, Group N Top mounts, JDM window visors, WRX side skirts, Seibon CF Hood

8. Sometimes I accelerate hard, sees redline daily, most of the time is granny driving.

[BruceyWV]

1. Super City in winter can get as low as 14 a tank. Regular city is more like 20~24 a tank. Highway is around 34~38 a tank.

2. 2000 Outback

3. SOHC, 60K on the engine.

4. Automatic

5. Mobil 1

6. No modifications to intake/exhaust

7. Stock size. Low Rolling Resistance

8. Front/Rear Sway Bars, Overload coils, Cross bars removed, Passenger mirror removed, wheels taped up, front end blocked off, smooth panelling along the under carriage (Minus around the exhaust), skid plates..

9. The engine was built and bored .040 over.

[cobcob]

1. City: 23.5

Highway: 25.7

2. 2000 2.5RS

3. SOHC coming up on 152k miles

4. 5MT

5. Penzoil

6. Bone stock until recently. Just installed Borla Rep UEL headers

7. Stock size Toyo Proexxes4's

8. brand new KYBGR2's in the rear on Monroe upper mounts.

9. Generally shift gears at 3000rpm. Cruise by the tach not the speedo. Typical highway speed of 67mph (3000rpm)