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Discussion Starter #1 (Edited)
i just bought a 2009 chevy cobalt sdn, auto with 45K miles from the dealer. i noticed i get about 200 miles to a full tank, at least half of that was highway miles. I dont know why this is, oil just changed and air filter changed, wheels are aligned. I read on a forum where this guy said he had the same problem with his, so he took his car somewhere and got a "trifecta" tune that took him from 200 a tank to 360 a tank. is that what i need to do, if so, where would i go for that and if i did tune it to get better mpg, would it void extended warranty i got with the car? i got a 60 month/60,000 mile warranty with it. any advice would be greatly appreciated! Thanks for looking.

Also, what is recommended tire pressure for this car? and im reading forums with people getting like 40 to 50 mpg with their 09 cobalts!, something wrong with mine, should i take it in???
 

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I think 40 to 50 is kinda out there, if you drove nothing but highway you could get 30+ if you kept it between 55 and 65. It's almost impossible here because of the traffic we get on the highway.
 

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I get in the 50's on the hwy doing 55-60mph but I also live in canada. There was a guy on here from the states that said he saw 46mpg one time but he was fully bolted and tuned. The automatics always get worse fuel mileage it seems. My average in summer is 7.2L/100km, while the best I've ever seen on an automatic is high 8's to low 9's
 

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Deven534 the best way to check if you have a problem or just bad driving habits is to take it on the highway, bring it to speed (60mph) keep it there reset your mpg on DIC. After about 5 minutes you should have your highway average. My 07 auto gets 6.7l/100Kms. (35mpg US) in the summer. If you get anything close to 30mpg this time of the year there is nothing wrong with your car.
 

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Discussion Starter #7
Ok I will take it on the highway and try that. But is there any commom issues with these cobalt that I have to be aware or that would affect mpg??
 

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When I changed my fuel filter I saw night and day. My mpg when from being stuck at 24.2 (no matter what-tune up, tires, etc) and jumped to 32.7 on the hwy. I have pics to prove it.
 

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you can tell without question when there is a fuel leak. Happened to me, reeked like fuel at stop and moving. Took it to the stealership- got the Special Coverage or whatever for a cracked fuel pump resevoir. But the OP would know if thats the problem
 

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Ok I will take it on the highway and try that. But is there any commom issues with these cobalt that I have to be aware or that would affect mpg??
If your HO² sensors go bad and you have a check engine light the ECM will keep engine in open loop and you will notice a considerable drop in mpg.

---------- Post added at 01:04 PM ---------- Previous post was at 12:58 PM ----------

When I changed my fuel filter I saw night and day. My mpg when from being stuck at 24.2 (no matter what-tune up, tires, etc) and jumped to 32.7 on the hwy. I have pics to prove it.
Can't see how a fuel filter could affect mpg, but if you say so and nothing else was done at the same time. Fuel mixture is controlled by the ECM depending on throttle position, air flow, air temperature and air pressure. If all your HO²s are working correctly your car should run at maximum fuel efficiency.
 

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---------- Post added at 01:04 PM ---------- Previous post was at 12:58 PM ----------

[/COLOR]

Can't see how a fuel filter could affect mpg, but if you say so and nothing else was done at the same time. Fuel mixture is controlled by the ECM depending on throttle position, air flow, air temperature and air pressure.[/QUOTE]

Yeah Coby I couldnt believe it either. The night before I drove from Ft. Campbell, KY back to Florida I changed the fuel filter and nothing else. It kept increasing, and by the time I got into Georgia the fuel range read 542MI (on a full tank).
 

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I changed a fuel filter one time and noticed amazing throttle response and power right off the bat. Maybe the filter was restricting fuel?
 

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Discussion Starter #14
I do not smell fuel at all while driving or parked. I will look at the spark plugs this weekend and let u know. Where is the fuel filter on my car? Some people were saying it only had one built in the fuel pump.....is there an in-line one at all?? If so, where
 

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Those ppl were dropped on their heads at birth. The fuel filter is right behind the fuel tank by the filler neck. If the plugs are bad or not AC delco it very well could be your problem. If they're bosch....well just replace then no matter how new they look
 

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A tune up helped mine a lot. My plugs were old.. but I did a full tune up at once. Went from 25mpg summer time to around 29.. that's what the dic said between highway and back road driving.

Sent from AutoGuide.com Free App
 

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Discussion Starter #17 (Edited)
So what should I all do in a tune up for my cobalt that has 45k and just had an oil change? And only use AC DELCO spark plugs, nothing else? And should I change ignition coil boots as well, or r they just one whole piece, like boot doesnt come off of ignition coil on cobalts?
 

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You shouldn't have to replace them. The plugs should be good at 45k but I would still change them. Only ac delco plugs. A tune up would be air filter, oil, spark plugs, fuel filter, make sure your tires are filled with the correct amount of air, ummm you could do tranny fluid too if you really wanted to but it wouldn't help your mpg

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