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2011 Forester
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34 Posts
Discussion Starter · #1 ·
I did some experiments today playing with the Trip B and got mixed results. It takes exactly 1 mile to register from 0.0 miles. When it flashes on the screen has it averaged the last mile or just what you are doing now? To me it seemed the later.

Anyway, has anyone determined on a Premium Forester ('11) with 4 spd Auto, what is the best speed for the best gas mileage???

My best guess is that maximum fuel efficiency can be had at "55mph" but to get there on time and keep up with traffic, 65mph is ideal. Therefor, I think that 60mph is the sweet spot. :Banane08: Agree- Disagree?
 

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Smooshed FOTY 2011
2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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5,732 Posts
71 mph. (at least on the older 4EAT XT's). That puts you right at 2950 RPM, which usually gets you the best "fastest" milage. If you go between 55 and 65 mph, you'll see your milage do very good (my best milage was over 100 miles only using 1/4 of a tank......driving at 55-65 through the snow in Chama, NM.)

 

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2004 Forester
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8 Posts
2500 rpm at 62.5mph on a 04 X using premium; 28-30 mpg (lots of hills) at this speed there is no downshifting by the automatic for long hills. Have about 155k on engine/tranny :biggrin: Not to bad for an awd with the nose of a subtly rounded brick.
 

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Ol' Timer
2006 WRX Spec-C 6MT
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5,961 Posts
50 mph. Our cars are VERY boxy, with poor aero work. I've consistently seen my best MPGs at that speed.
 

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Premium Member
2019 Crosstrek 2018 Forester XT
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15,013 Posts
Therefor, I think that 60mph is the sweet spot. :Banane08: Agree- Disagree?
Yea..that's pretty much it. You get more by going slower but its difficult. I used my own data and some extrapolation form fuel mileage curves.

MPH......MPG......Gal/Mi......Gal/Mi vs. 60MPH.....MPG vs 60 MPH

60........31.6.... .0316...........1.00 .................... 1.00

65........30.8.... .0325...........1.03 .................... .97

70........29.8.... .0336...........1.06 .................... .94

75........28.4.... .0352...........1.11 .................... .90

80........26.8.... .0373...........1.18 .................... .85
 

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15 FORESTER CVT
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314 Posts
Ahhhhhhhhh, how hard do y'all push the peddle? I drive primarily 2 lane roads and use my cruise whenever feasible.

 

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2008 LL Bean (4EAT)
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5,057 Posts
... that's pretty much it. You get more by going slower but its difficult...
"Sweet spot for best MPG" is so subjective, and has nothing to do with best mileage.

Several times I have gone 150 miles using only 1/4 of a tank, but that means nothing in terms of mileage (miles per gallon). However, it was done at 60 mph, and when the tank was low, dividing the gallons into the miles showed over 31 mpg.

That may be a sweet spot for covering distance with low mileage, but even lower mileage would be obtained at say 45 mph with its lower rpm and wind resistance.

However, the difficulty of maintaining 45 mph might not be a sweet spot for many.
 

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09 forester
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186 Posts
used my scanguage and got 4.5 - 6 L/100km at 55km/h in 3rd gear.
subaru brochure ( 10.4 city, 7.8 highway)

tested it a few times on same patch of road going in both direction.
i dont have the patience to test that speed for long stretch of the road.
 

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10 XT 4EAT
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893 Posts
71 mph. (at least on the older 4EAT XT's). That puts you right at 2950 RPM, which usually gets you the best "fastest" milage. If you go between 55 and 65 mph, you'll see your milage do very good (my best milage was over 100 miles only using 1/4 of a tank......driving at 55-65 through the snow in Chama, NM.)
there must be a gear difference between the SG and SH, as at 70mph in my '10 XT (auto) the engine turns at 2500rpm, unless you typo'd and meant 2590.
 

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2010 Forester Touring 5MT
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3 Posts
Agreed :)

50 mph. Our cars are VERY boxy, with poor aero work. I've consistently seen my best MPGs at that speed.
I've got almost 20,000km on my 2010 5mt Fozzie, and it's a great little car indeed. The average consumption is showing 9L/100km which works out to a little over 26Mp(US)g. I have yet to do a long trip on highways without hills and turns, but it never gets much over 9.5 unless my wife is driving with her heavier foot.

I also have a ScanGuage 2 hooked up, which is a great little tool for more accurate indications of when and how you actually burn the fuel. According to both of those, the best speed for distance is around 65km/h (40mph). As annoying as it would be to do so at this speed, the indicators say that you could in theory travel about 1000km/tank if you weren't faced with hills.

I really notice the difference of every mph faster than about 50, and they cost a lot of fuel .. so if I'm trying to save the juice, I just slow down.

It would be nice to have a more aerodynamic shape, but the rest of the car is just fantastic :) (except for the lousy stereo/speakers)

My mom is just considering flipping her 2001 for a 2010 AT Fozzie, so it will be interesting to see how much difference there is between the MT and AT.
 

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2001 Forester Dual-Range Manual
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614 Posts
Well for me in my 5M/T SF 2.0L my sweet spot is between 50-60MPG and I get 6.5-7.5L/100km.

I get about 110miles out of the first quarter of the tank and 90 out of the rest and 30 with he light on, on the highway at 60MPH. But as soon as I hit 70MPH or higher I get about 8-9L/100km on the highway. I usually sit on 80MPH with cruise control on.
 

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2008 LL Bean (4EAT)
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used my scanguage and got 4.5 - 6 L/100km at 55km/h in 3rd gear... tested it a few times on same patch of road going in both direction....
My ScanGauge shows 45 mpg for stretches of road at a steady 45 mph. The display is lower at any lower or higher speed, so 45 mph might be the sweet spot for best mileage. The figure of 45 mpg is only a brief reading to see where the engine uses the least gas, and that mileage can only be maintained for a few moments. Lifting the foot causes the display to shoot to 9999 mpg, and gently resuming 45 mph drops the display to 13 mpg. I suspect if one tried to maintain 45 mph for a whole tank, and then divided the miles by the gallons, the result would be around 35 mpg.
 

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2005 Forester XT 4eat
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My ScanGauge shows 45 mpg for stretches of road at a steady 45 mph. The display is lower at any lower or higher speed, so 45 mph might be the sweet spot for best mileage. The figure of 45 mpg is only a brief reading to see where the engine uses the least gas, and that mileage can only be maintained for a few moments. Lifting the foot causes the display to shoot to 9999 mpg, and gently resuming 45 mph drops the display to 13 mpg. I suspect if one tried to maintain 45 mph for a whole tank, and then divided the miles by the gallons, the result would be around 35 mpg.
When I'm driving around town with lots of traffic lights, I try to drive 35-45 mph in OD as much as possible, and I get the same fuel economy in the city as I do on the highway. I would say 45 mph would be the most efficient speed to drive at IF you can keep it in overdrive with TC lockup.
 

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2011 Forester
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34 Posts
Discussion Starter · #15 ·
Thanks for all the replies. It sounds like our on-board mpg scanner is not very accurate. Everyone has confirmed what I suspected which is, given the boxy shape of the FOZ, the sweet spot is about 60mph- for ideal fuel economy, even a little below that. Where I live however, going 50-55mpg on the highway is dangerously slow so I'll stick to about 60-62mph. I might get a little less MPG but I'll arrive sooner and more safely which at the end of the day matters to me more than the extra $3 I'll save at the pump. :woohoo:
 

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2007 Forester XT manual
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1,452 Posts
there must be a gear difference between the SG and SH, as at 70mph in my '10 XT (auto) the engine turns at 2500rpm, unless you typo'd and meant 2590.
My 07 XT 5 speed indicates exactly 2750rpm @ 110kmh (68mph)

There is no change in gear ratios between the SG and the SH but the SH is slightly taller geared because it gets one size larger tyres - 225/55 17 v 215/55 17 on the XT and 215/65 16 v 215/60 16 on the X. Changing tyres on a car won't change the speedo/tacho relationship but will make your speedo either more or less accurate depending on the tyre size.

BTW I reckon the most economical speed is around 60-70 kmh but who the hell is going to sit on that for any length of time?
 

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2001 Forester Dual-Range Manual
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614 Posts
^ So true. I would'nt sit on 60-70km/hr on the highway. About 105-120 is good for me and the fuel is still excellent.
 

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2010 2.5X Prem 5MT
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I have the 5 MT and do mostly rolling hills on my normal drives and what I've found is the the faster the better upto at least 65mph. I can shed a few mph going up hill and keep the mpg on the scangauge up fairly good. If I slow down and maintain speed on the hills or use cruise the numbers go down.

I've only got about 2500 miles on it now and no long trips so I'm not sure about flat land mpg.

Kevin
 

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Smooshed FOTY 2011
2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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5,732 Posts
there must be a gear difference between the SG and SH, as at 70mph in my '10 XT (auto) the engine turns at 2500rpm, unless you typo'd and meant 2590.
No typo, at 71mph the needle is just under 3000 rpm on the 04 XT 4EAT's. I'm sure they made adjustments to the final drive/ratios in the later models to keep the RPM's down lower and increase highway fuel consumption. Once you venture into the 3k's and higher in the SG XT's, they start to drink fuel a bit more briskly.
 
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