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Could my car be running rich?


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Did a little search and couldn't find anyone with a similar question so thought I would post.

 

So far my cars done 7,000km and I am averaging 11ltrs/100km calculated.

 

The Cars Computer average reads around 10.8ltr/100km. Not that happy with this as I drive 50km to work everyday and 90-95% of that drive is travelling at a Highway speed of 100km-115km. Even with the CC on the Car averages 10.8-11ltr/100km.

 

Today I noticed that when I let off the gas and coast the cars computer reads the current 0.2 Ltrs/100kms. Which I expect is the lowest it will read without ---- showing.

 

Towards the end of my journey 45kms in after a traffic light stop. When coasting to the next turn the average starts at 0.2ltr/100kms and then starts to raise to sometimes 8ltrs/100km without my foot on the gas pedal.

 

Anyone had this problem? Is it worth talking to my Subaru dealer about this or am I just being daft.

 

I love this car and have only driven it to red line once or twice at best after the break in. Therefore you would think that the average ltr/100km would be lower.

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When you are coasting, the engine uses very little or no fuel. On my 5MT, the instantaneous MPG reading always goes to 99.9mpg when coasting in gear. I don't find watching the instantaneous MPG reading to be terribly useful. It is more of a right foot indicator than anything else.

 

If I converted things correctly, 11L/100km = 21.4mpg. That sounds low for 95% highway driving. I average that for half highway/half stop and go city driving.

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Yeah 21Mpg. I figured that was to low for highway. I did try and push it a ltttle harder, some quicker than normal starts, and and few overs on the highway,the average over the tank went to about 12.5ltr/100km. Doesn't seem that different. What concerned me was the increase in litres used when coasting which didn't sound right, unless the car is hunting for some reason.
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Fuel consumption has to raise to the car doesn't stall. With a 5MT, if you coast in neutral, you won't see 99.9. It is only when the wheels are "driving" the engine. As you slow down, eventually the ECU will call for fuel to maintain idle RPMs. I am just guessing this is what you are seeing. My 5EAT experience is limited to a few days of loaners.
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For mixed driving, mostly highway, I'd say 21+ is normal. I ave. 19-19.5 with the auto tranny pretty much no matter what I do. Are you using Cruise on the highway? ..that seems to hurt my mpg by 10-20%

 

If you're not using cruise, and you're driving consistently at 100-110kph, then yea, I'd say that's a bit low, but not "crucially" low. It should be possible, if babying it at 60-70mph to get at least mid 20's, if not high 20's.

 

Have you noticed a change in your fuel efficiency lately or has it always been around this level? If you've noticed it decline significantly, it might be worth checking out. There are a few things that can cause the car to run rich like the MAF & 02 sensors, but I suspect if they're off, it's not by much and that's just about what you can expect from a 250hp vehicle.

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So then mine should go to 0.2ltr/100km and stay there.

 

I have a 5mt, so I can't say this from experience, but I would call your brief spike in l/100 normal. The car has to downshift as you approach the light, and even though you are not physically touching the gas pedal, the computer will blip the throttle for you to allow for a more seamless downshift. The spike in L/100 you see is just the result of that brief throttle-blip.

 

As far as your fuel consumption, I have been calulating mine since new (and comparing the overly optimistic computer) I have averaged 10.5 L/100 (22 mpg) over the 12500km I have put on the car (75% highway) since I picked it up on Dec 2.

 

One thing I have noticed is that my fuel mileage has trended downward since new by about 1L/100 starting at about 5-6000km - I'm hoping the trend continues!

 

As above, I would expect a small penalty from the 5EAT unless you are doing 100% highway, as you have a slightly taller 5th gear over the 5mt.

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What octane rating are you using? I'm using 93, am still breaking in and am averaging 24+ on the highway, 22+ all around.

I've been using 91 with a mix of 94. Probably an average of 4 to 1

I don't think the blip is from a down change as it is a steady increase over a 5 seconds or so period. It reads 0.2Ltrs/100km from 100kph down to about 60kph but then steadily increases to 3.4 then 5.4 and sometimes 8.4. It's strange as it didn't happen before and it doesn't level off again.

My previous Kms per tank have been around 420-500km, which I think from reading posts is about normal. So far this tank looks like it might break 500 before the light. I'm just above 1/2 tank and it's at 250km. I’ll do the maths when I fill up next to see average mpg.

I think I would die if I was getting 13mpg and driving like a granny.

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I've been using 91 with a mix of 94. Probably an average of 4 to 1

 

I don't think the blip is from a down change as it is a steady increase over a 5 seconds or so period. It reads 0.2Ltrs/100km from 100kph down to about 60kph but then steadily increases to 3.4 then 5.4 and sometimes 8.4. It's strange as it didn't happen before and it doesn't level off again.

 

My previous Kms per tank have been around 420-500km, which I think from reading posts is about normal. So far this tank looks like it might break 500 before the light. I'm just above 1/2 tank and it's at 250km. I’ll do the maths when I fill up next to see average mpg.

 

I think I would die if I was getting 13mpg and driving like a granny.

 

I'm getting to the point where I feel like I should just push it as hard as I can all the time because my fuel mileage is going to be horrible no matter what...

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