[grace1414]

A newbie to the forum so please be gentle .... :biggrin:

Vehicle is a Forester 2.0D Premium - 6 speed manual, 22,000Km on the clock.

For my 2011 2.0D Subaru claimed just 5.7L/100km fuel economy on the open road and an average of 6.4L including around town.

I know we treat these figures with the contempt they deserve but in a laboratory somewhere they did it once .....

Fact is, I actually get 6.4l/100Km around town without much effort at all. Single passenger, no cargo and mild road rager. Am VERY happy with that.

Problem is, when I do a long highway trip, say 1,200Km at around 100 to 110Kph (GPS) with just a bag of clothes (not heavy denim) my fuel economy drops to almost 7.4l/Km (using cruise control).

These figures I am quoting coincide with what the car tells me but I keep a spreadsheet of every tank I use and it agrees with the car (as near as).

The car has no external options like roof racks, bull bars etc fitted - it is stock standard so the drag coefficient has not been modified in any way.

I always check tyre pressure with my own guage I carry, especially before any long trips. I use the vehicles pressures as a guide and then consult the tyre manufacturer (yokohama geolanders).

I tried changing the air filter (stock paper replacement first) which made no difference.

Firstly, has anyone else experienced this anomaly of better fuel economy around town? and

Secondly, where do I start looking for issues?

The vehicle was just in (prematurely) for its 25K service to Subaru. I mentioned it to them. They drove the car with analyser attached (OBDII) and couldn't see anything wrong.

Not sure what to do next

Have a 4,000Km trip coming up in two months. Would like to get it sorted beforehand as it could save me a few dollars in diesel.

Would love to hear some ideas (relating to this issue only thanks)

 

[R5oss]

Would love to hear some ideas (relating to this issue only thanks)

Welcome grace1414, as for the above request, SF.org tends to 'chuck in' with all sorts of frivolity :Banane35:, so if you're a sensitive soul, tough :biggrin:

What tyre pressure have you set.
Any alignment/tracking issues.
Are you driving this diesel like previous vehicles you've owned, ie: low revs for best economy.

 

[dpm]

for economy, cruise control may not be your friend. Plus the extra drag of going from 100k to 110kph is noticeable. What about changes in altitude? Wind?

My 09 is a bit differrent- only gently cruising in the 50-60mph bracket net brilliant economy; round town and about 70mph and it drops rapidly...

 

[monbeg]

Not sure what is going on there Grace.
I average between 6.2 and 6.4 around town and the average for the just over 12000km I have done is 6.4.

Of that 12000km around 3000 has been through hills etc including East Sale in Victoria to Albury over Mt Hotham etc.

Very rarely do I ever use 6th gear, normally 5th even at 110kmh, I like to keep the load off the engine and generally run 2000 to 2500 rpm.
Don't over rev or overload a diesel engine, make use of the gear box.

I would suggest getting a good service done and turn the radio down (if you have it up) and listen to your engine.

Just my 2 cents worth.

 

[Duderotomy]

What sort of mileage does it see at 100km/h then? Clearly 110 isn't where it likes to be...

 

[Amboscott]

I am guessing the AirCon is also on.
The foresters have all the aerodynamics of a tin shed.
Yes I can get <6.0 l/100km doing a smooth 60-80 commute but a real 110km/h (118 on Subaru's optimistic speedo) will see it go up to the 7s.

No getting around the fact that it is a realatively big box to push through the air and the the resistance squares as you go faster. i.e. 141 kmh is twice as hard as to push through as 100 kmh and 200 is four times.

 

[grace1414]

Welcome grace1414, as for the above request, SF.org tends to 'chuck in' with all sorts of frivolity :Banane35:, so if you're a sensitive soul, tough :biggrin:

What tyre pressure have you set.
Any alignment/tracking issues.
Are you driving this diesel like previous vehicles you've owned, ie: low revs for best economy.

tks for the feedback (off the rails for a little)

tyre pressure currently running is 35 psi (on the high end being unladen mostly)

i cant detect any tracking issues and handling seems symmetrical ( same into left or right corners) but i am getting it checked shortly anyway prior to this long trip.

i drive diesel vehicles at work so am familiar with the lazy driving approach ...

i am finding it a challenge to get these figures down, it's a fun experience with the vehicle ... they put in the eco gauge and the current (average) fuel consumption indicator ... now it's a challenge to get the figures as low as possible .... if anything i probably labour the engine a little. ... but that can't account for the dip in figures at highway cruising where they claim lower 5.7l/100Km

i dont care if i dont get to 5.7 .... problem i have is my consumption goes up on the highway

 

[grace1414]

for economy, cruise control may not be your friend. Plus the extra drag of going from 100k to 110kph is noticeable. What about changes in altitude? Wind?

My 09 is a bit differrent- only gently cruising in the 50-60mph bracket net brilliant economy; round town and about 70mph and it drops rapidly...

i think it's been proven many times over now that cruise control is the better for consumption, i will vouch for that from my previous 4 cars ....

even so, the cruise control COULD NOT make my consumption worse on highway (sits in sixth gear all day)

altitude? this is western australia, we dont have any altitude .... zero change
wind? no, cant account for the severity ... thanks

 

[grace1414]

Not sure what is going on there Grace.
I average between 6.2 and 6.4 around town and the average for the just over 12000km I have done is 6.4.

Of that 12000km around 3000 has been through hills etc including East Sale in Victoria to Albury over Mt Hotham etc.

Very rarely do I ever use 6th gear, normally 5th even at 110kmh, I like to keep the load off the engine and generally run 2000 to 2500 rpm.
Don't over rev or overload a diesel engine, make use of the gear box.

I would suggest getting a good service done and turn the radio down (if you have it up) and listen to your engine.

Just my 2 cents worth.

thanks for the feedback .... i know victoria well, spent 12 years there ...

but this is WA and as I mentioned earlier it is a large and flat slab of red dirt which begs for eight gears .... my 6th gear drops revs around 400 rpm (will check that) ... it no good for overtaking but the long flats (which is 90% of this place) it works great

i like to run it also 2000 to 2500 (max), agree totally with that .... it works very well in this range though I rarely need 2500 due to the lack of hills (i did see one once, just east of perth, but by the time i rolled down the window to admire the lump i had passed it and was back on the flats again, sigh) .... I drive by ear, always have so every noise that engine makes is registered with me.... and until i resolve this issue i will be sticking with talkback radio so the music doesnt mask any issues ..

thanks

 

[grace1414]

I am guessing the AirCon is also on.
The foresters have all the aerodynamics of a tin shed.
Yes I can get <6.0 l/100km doing a smooth 60-80 commute but a real 110km/h (118 on Subaru's optimistic speedo) will see it go up to the 7s.

No getting around the fact that it is a realatively big box to push through the air and the the resistance squares as you go faster. i.e. 141 kmh is twice as hard as to push through as 100 kmh and 200 is four times.

so you see similar figures... you're the only person to quote a highway figure so far thanks

my commute has a large component of cruising 80Kph which yields 6.4 to 6.2 l/100Km (this figure subaru claim for city cycle)

it still begs the question, on what highway (highway cycle) could Subaru claim 5.7l/100Km ... i'm going to continue to torture my service manager, because i can

tks

 

[dpm]

You are mistaken to assume cruise is better UNLESS there is absolutely no traffic, no inclines either way, etc. IMO.

I run scangauge for instantaneous numbers and see downwards trends caused by cruise, regens, and low rpm lugging.

My lifetime average (115k miles)is somewhere around 42mpg (imp). Hand-calculated individual whole tanks range from a low of 36 (ladders on, 75mph will do this) to a high of 47 (gentle holiday sightseeing). Bearing in mind that this is a small island and I couldn't sit on cruise for more than about 70 miles at a go, I can certainly watch cruise chip away at a good mpg figure as it fails to pre-emptively react to conditions.

what gear are you in at 80kph? I'm thinking you might be trying too hard to keep the revs down. Consider DPF regen activity too, if you're being extremely gentle.

 

[R5oss]

grace1414, other than the fuel used, the diesels you drive at work sound as if they are "old school". IE: as you've stated, you run low revs for best economy & lazy driving.

Our collective experience of Euro4/5/--- onwards is that low revs no longer produce the economy or driving that we've become used to when driving older generation diesels. At 80Km/h in your Forester you will only need 4th with the engine revs in the 2200-2600 range. At 100Km/h you'll still be in 4th !.

So don't be afraid of letting the rpm go past 2500, and accept that there are too many (on-road) gears in the 6MT. Unless of course you are above 130Km/h !.

Mike.

 

[Amboscott]

"my commute has a large component of cruising 80Kph which yields 6.4 to 6.2 l/100Km (this figure subaru claim for city cycle)"

On the flat with no wind you should be getting 5l/100 at a steady 80kph. This is in 4th or 5th.

 

[Amboscott]

Be aware the "highway" economy that is quoted is NOT a 100 or 110 k/hr cruise it is "extra urban’" component has a relatively high (compared to the urban)
average speed (63 km/h) and a peak speed of 120 km/h. It is not a typical ‘highway’ cycle as it does not maintain a relatively constant speed over an extended period of time


See this PDF for a graph.
http://www.mlit.go.jp/kokusai/MEET/documents/MEETFUM/S4-Australia-sup3.pdf

 

[Turbaru]

When i had my diesel, my best run was 4.6 per 100km. The needle was sitting on 100kmh mark, with cruise on. Some overtaking (max speed 150kmh). Flat ground, no hills, mountains, etc.

 

[SambOz]

G'day Grace, we have a 2010 diesel For with 62,000km on it and live out of town so it never gets started to go under say 50km's and more often 100km's.

It sat at 6.2l/100 for say 50,000km and on a trip from near Sale to north of Mt Isa last year sitting on 100 to 105 kph (GPS speed) it returned 6.2l / 100km over the 7,000km's ( approx ). AND WE HAD DENIM IN THE BAGS..LOL

During 2013 it has improved to 5.6l/100km consistently which we are very pleased with.

We find 6th gear to have quite adequate acceleration from a reasonable speed, ie, not under say 90/95 kph.

Do you jam your foot down hard going thru' the gears or just let revs built gently, do you drive up to corners hard and then have to brake ?

 

[charliehorse]

I get 7.4 on motorway at steady 130kph indicated with cruise on. I get 6.2 if I really try.
Haven't been able to better this but I just moved from a dead auld auto Pathfinder
and I am like a young lad at Christmas with all the revs and power.
Denims on but no bags :icon_wink:
I used a product called Dipatane (sp?) for a few tanks and it seemed to make a difference.

 

[GrumpyUnclePete]

Greetings fellow rattlers,

We joined the tractor driver's fraternity a couple months ago and have so far been loving it.

We've had it just long enough to get an idea of fuel economy figures, so I thought I might chime in with our data FWIW. 2010 Fozza rattler prem with 80,000 k's on it.

It's normally used for ferrying the kids to school where it returns an ave of 6.6l/100 per tank as reported by the car. It's hard enough to get the wife to reset the trip meter each tank let alone record how much fuel she filled in and how many k's she's driven. So we have to believe the car.

Recently returned from a 5000km interstate family trip (take that DPF!!) where I was hoping to get some solid data but well, kinda failed cos it just varied so much. Trip was Adelaide, Bendigo, Mallacoota, Bateman's Bay, Canberra, Sydney, Armidale, Narrabri, Hay, Waikerie, Adelaide.

We loaded up with 2 adults and 2 teenage kids - and all their luggage plus roof pod. I do not drive for fuel economy. I drive to get there ASAP. But I agree that it's wind resistance that's killing us. I expected great things after averaging 6.6 around town but it was never gonna happen. There's also a marked difference going from 100 to 110kph. I tend to drive 10% over what the speedo says too, as it lines up better with GPS speed.

So anyway, to Bendigo it was looking like about 6.8l/10 would be the figure. Then from Bendigo to Mallacoota we had a tail wind and a lot of 100kph zones and achieved 6.2l/100. I almost got excited there for a moment. From there it was back to around 6.8 around most of NSW. Until coming home across the Hay Plains. Head wind. 110kph. Oh dear. Warm day too - so AC cranking. So this was definitely worst case. It settled to 8.0 while crossing the Hay Plains. That's the worst I saw. As soon as the wind backed off the ave decreased for the rest of the tank to around 7.6 when we got home.

Not sure what the ave over 5000 k's was but I'll check tonight.

No DPF issues for us so far...
UnclePete

 

[GrumpyUnclePete]

Checked last night - over our 5000 km journey we averaged 7.0l/100. Not bad I thought, considering the load and the not always favourable conditions.

 

[SambOz]

A lot of all wheel drive owners would never see that economy for that trip and be rapt if they could. No doubt the roof pod and A/C dragged it back a bit but I would say that is an excellent return. :icon_cool: