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MPG is greatly decreased

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Old 01-11-2011, 11:51 PM
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MPG is greatly decreased

I have a 2008 auto/Sport/55,xxx miles. Recently I noticed that my MPG is greatly decreased. Usually I get around 150-175 miles when it come to half a tank. Now, I ONLY get around 120-140. Anyone have the same problem ?
 
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Old 01-12-2011, 02:18 AM
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Winter gas blend? Mine's more or less been the same as well =/
 
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Old 01-12-2011, 02:35 AM
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check spark plugs, oil, oil filter, air filter, gas(type of gas), injectors... geeze theres so much but doing all of those might eventually lead you to the problem!
 
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Old 01-12-2011, 02:48 AM
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Mine has also... But I think it's due to going from 185/55/16's to 205/45/16's on GE Wheels. Sucks man... I'm only getting like 25-26mpg now combined. Never get more than 250 miles to the tank.
 
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Old 01-12-2011, 03:04 AM
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Like stated above, it good be a winter blend for the fuel you get. Never the less check your tire pressure, the air filter, oil level, etc.

If you really want to see an increase in fuel economy, use the paddles in S. You'll be able to control your shift points as well as the rate the torque converter closes by carefully manipulating the throttle. With minor hypermiling techniques like coasting to a stop, anticipating lights, and lightly accelerating (all with respect to the traffic) I easily averaged 37 MPG (half tank around 200 miles) when I had the original 195/55R15 Dunlop SP31s in my A/T Sport.
 
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Old 01-12-2011, 04:28 AM
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I'm getting lesser mpg also. I found it hard getting 40mpg since I switched to 195/50/15. I was getting 37-39mpg on average and 40+ when hypermiling. Now I get 34mpg as low as 32mpg it sucks! OEM tire size is the way to go.
 
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Old 01-12-2011, 09:06 PM
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I am hitting 220 miles at half tank, 360 when the gas light comes on. Over 420 miles when I put gas in. But only get 33 mpg or less highway going 75mph. I get these miles by shaking the car side to side, add about .2 gallons, shake, add, shake, add... I can put in 2 plus gallons extra with this method. Otherwise, my gas light comes on at 260 miles if I stop pumping at first click! I hate stopping for gas.
 
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Old 01-12-2011, 09:23 PM
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could it be my tires ? I changed it to 205/45 (PSI:37)
I do changed my oil/filter regularly though. Have not change any spark plug since I purchased the car.
 
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Old 01-12-2011, 09:24 PM
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Originally Posted by rocksnap
I am hitting 220 miles at half tank, 360 when the gas light comes on. Over 420 miles when I put gas in. But only get 33 mpg or less highway going 75mph. I get these miles by shaking the car side to side, add about .2 gallons, shake, add, shake, add... I can put in 2 plus gallons extra with this method. Otherwise, my gas light comes on at 260 miles if I stop pumping at first click! I hate stopping for gas.
what size is your tires ?
 
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Old 01-12-2011, 09:25 PM
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Originally Posted by paomatic
check spark plugs, oil, oil filter, air filter, gas(type of gas), injectors... geeze theres so much but doing all of those might eventually lead you to the problem!
I changed oil/filter when it's schedule by dealer. what do you mean type of gas ?
 
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Old 01-12-2011, 10:53 PM
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Originally Posted by Super Mario
Mine has also... But I think it's due to going from 185/55/16's to 205/45/16's on GE Wheels. Sucks man... I'm only getting like 25-26mpg now combined. Never get more than 250 miles to the tank.
Correct, wider tires = more grip but less mpg
 
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Old 01-13-2011, 01:11 AM
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I recently changed my tires to Yokohama AVID Envigor, noticed a few MPG drop, tire PSI still 40 which is what i used on the dunlops. tire size still stock at 195/55/15. The OEM Dunlops, even though they suck at everything else, especially wet driving, are low rolling resistance tires, so they specialize in getting better MPG. Enjoying the new traction, it's worth it, even though I am getting around 34-35mpg instead of 37-38mpg
 
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Old 01-13-2011, 08:13 AM
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Originally Posted by SleepyNyte
I recently changed my tires to Yokohama AVID Envigor, noticed a few MPG drop, tire PSI still 40 which is what i used on the dunlops. tire size still stock at 195/55/15. The OEM Dunlops, even though they suck at everything else, especially wet driving, are low rolling resistance tires, so they specialize in getting better MPG. Enjoying the new traction, it's worth it, even though I am getting around 34-35mpg instead of 37-38mpg
Maybe I should increase my PSI to 40 and see if it improve any... I also got Yokohama 205/45/15
 
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Old 01-13-2011, 11:49 AM
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Originally Posted by InternDoc
what size is your tires ?
I have the Sport, so 15" tires.

And its not so much the tire width with more grip that drops milage. Its the added weight/rotational mass that takes more engine power to spin them. Thats why the Fits with better milage have 14" wheels/tires. Less rotational mass to spin...
 

Last edited by rocksnap; 01-13-2011 at 11:53 AM.
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Old 01-13-2011, 01:35 PM
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Originally Posted by rocksnap
I have the Sport, so 15" tires.

And its not so much the tire width with more grip that drops milage. Its the added weight/rotational mass that takes more engine power to spin them. Thats why the Fits with better milage have 14" wheels/tires. Less rotational mass to spin...
Uh.. that is not necessarily true.

You are neglecting rolling friction between tires and tire width definitely plays a part.

Also a 14" wheel has a shorter final drive ratio which raises engine speed across the board.. this consumes more fuel.

When you are steady state cruising wheel weight is not as big a factor as you are assuming. It takes very little power to maintain cruise speed. Aerodynamic drag, drivetrain loss and rolling friction are the big enemies here.
 
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Old 01-30-2012, 11:17 PM
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I'm having this EXACT issue.

Did you ever figure out what it was? I noticed it starting in October, and it hasn't gotten better. I changed the battery in September after it died on me. And the tires in October. And I do regular oil changes, filter changes, etc. If you solved it, I can't wait to hear what you did!
 
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Old 01-30-2012, 11:57 PM
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cold weather. cold air = more air entering engine = your car compensates by giving more fuel
 
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Old 01-31-2012, 12:02 AM
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Cold weather? This is my fourth winter with the car. First time this has happened. It has to be more than that.
 
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Old 01-31-2012, 12:08 AM
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cold weather. cold air = more air entering engine = your car compensates by giving more fuel
 
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Old 02-01-2012, 10:23 AM
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tire size

Originally Posted by InternDoc
what size is your tires ?
I have the stock Sport size. 195/55-15 I think.


Also, depending on what part of the country, or not, they may have switched to that damn ethanol gas which will drop your MPG. Just a thought...
 

Last edited by rocksnap; 02-01-2012 at 10:26 AM. Reason: just because


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