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Old 02-03-2013, 10:41 AM   #1 (permalink)
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Default Help with mileage

Hello All, Having mileage issues. 2010 cvt premium 2.5, 28000 miles. My first winter with this car. Mileage in spring and summer was 25-29 highway with ac on. I was happy. Lately , mileage is slipping, now down to 12.6 average on the computer. What could be wrong? Is there some type of issue I am not aware of? Tire pressure is good, cannot imagine what is happening. Thanks All, Dominator
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Old 02-03-2013, 10:45 AM   #2 (permalink)
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Is it cold where you drive?
Winter mpg drops because the engine takes longer to warm up and the PCM keeps the mixture rich longer.
Driving habits is a biggee. Do you warm the car up or let it idle longer in the cold?
Do you use the car more for short trips?
Driving in snow drops mileage due to the added drag of pushing snow away from the tires.
Lubricants are thicker in the cold and add a bit of drag.
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Old 02-03-2013, 10:53 AM   #3 (permalink)
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MPG will drop a little in the wintertime, but over 50%? That's very abnormal.

Have you confirmed with calculated MPG that the OBC is giving you a relatively accurate MPG? I would verify that first; there could be something wacky with the OBC.

To have the fuel efficiency drop more than 50%, you would have to have low tire pressure, extreme cold weather and short distance trips, a crazy ethanol gas mixture, the car loaded with weight, rooftop cargo, etc. Basically a combination of everything that negatively affects fuel efficiency...all at the same time.
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Old 02-03-2013, 11:23 AM   #4 (permalink)
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I can understand 12 mpg if you're doing a lot of stop-and-go or short trip driving, which I would consider severe vehicle operation.
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Old 02-03-2013, 04:36 PM   #5 (permalink)
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My car is hovering right around 18 MPG average right now. I have a 2 mile commute to work, and it is on a 50 MPH limit (60 MPH traffic) rd with plenty of stop lights. Basically, you're on the gas or the brake at all times. That's only a slight exaggeration. My engine is not even heated up by the time I get to work.

I your commute is worse than mine, it might be possible to get 12 MPG. You'll want to calculate it by hand when you fill up, though... Just in case the computer is way off for some reason.

Other than that, I might look for sticky brakes or something else adding a lot of drag.
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Old 02-03-2013, 04:55 PM   #6 (permalink)
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Its really been cold here in Wisconsin and most days I drive about 6-8 blocks and drop off my kid to school, then about 1 mile to work....all city (under 35 MPH) driving....if I don't get a good highway drive in my mileage will sit in the low teens....and idling does really kill it, but when I have short trips I want it to run a little longer so I let it idle some.

Depending on your commute I can believe it is possible.
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Old 02-03-2013, 05:14 PM   #7 (permalink)
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Wow. I too was getting 25-29 hwy and with winter fuel I'm lucky to 26. The worst it has got on my daily drive was 22mpg.

You will see a drop in the winter but 12 mpg? Are you the only one that drives the car? Unless your racing at every stop or driving in snow, towing, it's hard to see.
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Old 02-03-2013, 05:36 PM   #8 (permalink)
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So since I didn't see anyone else post/allude to it, I'll play devil's advocate.

While the car is relatively young (mileage), try cleaning off your o2 sensor. If you got bad gas, it ran rich for some other reason, something like that, a mixed signal from the o2 sensor might cause the car to run rich before you get a CEL notifying you it's completely dead. I've had that happen before, and I experienced a roughly 35% loss in mpg. That, coupled with cold and city driving, could certainly cause a combined 50% loss.

Also, check other things; vacuum (small leaks can cause issues like that), run some injector cleaner, etc. Usually this is something you'd check on older cars with higher mileage, but again, it's possible something got gunked up, is sending a strange signal, and the car is running rich to compensate.

Just a thought.
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Old 02-04-2013, 02:08 PM   #9 (permalink)
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I too have a '10 Outback Premium 2.5 that I just got in October so I don't know what my mileage is in the "summer". I live in upstate NY so we've had snow and cold. I was getting about 24-25 calculated manually and now am at 22-23 so while there's a drop I'd have a hard time accepting a 50% loss in mileage.

One thing I do notice is when I start driving and it's cold the tach is usually around 3-4k depending on how much I step on it from a stop and even when I'm cruising on the highway my tach sits around 2400-2600 at cruising speed (60-70mph) until the car warms up sufficiently then the tach drops down to around 1800 - 2100. Perhaps you have an issue that your engine rpm's isn't dropping down.

Have you reset your trip odometer lately? That's what the onboard system uses to calculate your mileage. Reset it at the next fillup. And as a double-check calculate your mileage manually rather than go by the onboard system.

And a real dumb question, you're not smelling fuel around your car all are ya? Nothing leaking?
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Old 02-04-2013, 05:15 PM   #10 (permalink)
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Quote:
Originally Posted by skondolf View Post
And a real dumb question, you're not smelling fuel around your car all are ya? Nothing leaking?
A leak wouldn't show up as low fuel economy on the display.
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