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Chevrolet Cobalt Real World MPG

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    tsjaytsjay Member Posts: 4,591
    I filled up the Cobalt and then drove it to the Nashville Airport, about 100 miles one way, then drove it back after returning from my vacation. I did a little local driving and then drove to work today.

    I filled up at lunch time and the mileage calculated out to be 32.8 MPG. The DIC was saying that my average was 32.1 MPG, so I actually did a little better this time than the on board computer indicated.

    Considering that I was driving up to 75 MPH on the trip to the airport and back and that I had a little local driving in the mix, I am not disappointed with 32.8 MPG.

    Tom
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    micwebmicweb Member Posts: 1,617
    There are variations in fill-up from tank to tank and you have to track several tanks to start getting a feel for whether the DIC is "high" or "low." Mine read consistently high. I used to get similar to higher mileage with my '06 Cobalt coupe, stick shift. Chevy really builds fuel efficient cars (especially considering that the Cobalt has the largest stock engine in its class and most horsepower).
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    tsjaytsjay Member Posts: 4,591
    I agree completely, Mic. Several tanks of gas should be averaged together for a good read on gas mileage, because, like you said, there will be variations in how "full" we get the tank from one refueling to the next.

    Tom
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    tsjaytsjay Member Posts: 4,591
    I got 28.9 MPG by manual calculation on my last tank of gas. The DIC was showing 30.1.

    I'm pretty happy with the 28.9, considering that there was the usual mix of city and highway driving.

    I hope to take a 275 trip this weekend, and it will be mostly Interstate. I'm anxious to see what kind of mileage I will get on that trip.

    Tom
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    tsjaytsjay Member Posts: 4,591
    Dave:

    I'm thinking very seriously about going with Mobil 1 on my first oil change. I switched a 94 Z28 Camaro to Mobil 1and gained 5% on MPG. I was in the habit of checking gas mileage on every fill-up, and I had a LONG history of gas mileage that showed that I was getting 20 MPG on that car. After switching to Mobil 1, I continued to check mileage on every fill-up, and the average MPG went up to 21 over several tanks.

    I have also been one to change oil religiously at 3000 miles, but I now think that I have wasted a lot of money on oil changes. I plan to use the Oil Life Monitor on the little Cobalt to tell me when to change the oil. I don't think I will go more than 7,000 miles, regardless of the OLM reading. Is that a good plan? With the synthetic oil, though, should I let the car go to 10,000 miles, if the OLM says I can?

    Tom
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    gtodavegtodave Member Posts: 12
    tom,
    i usually change my oil before it gets 3000 miles on it. like you, i think than i have been wasting money considering how much better todays oil holds up. the 12 year old cavalier i traded in had 172,000 miles on it and synthetic oil from the very first oil change. i have a friend that changes his oil every 10,000 miles if he is lucky. he gets the same longevity out of his cars as i get from mine. i think we have been wasting money from my point of view, which is that of a frequent oil changer mind you. since i'll be using mobile 1 from here on out, i'll have no problem waiting for 10,000 miles if that's how long it takes...
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    tsjaytsjay Member Posts: 4,591
    We are going to need to be sure to use long life oil filters, if we are going to go 10K miles between changes. What filter do you plan to use?

    Tom
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    poncho167poncho167 Member Posts: 1,178
    Stick with the AC/Delco, they are proven and designed with metal internals not paper, and the proper valving.
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    tsjaytsjay Member Posts: 4,591
    I averaged 33.7 MPG for my 475 mile round trip to central Illinois and back today. That's not too bad.

    I would have done a little better if I had cruise control. I looked down at the speedometer and caught myself doing close to 80 MPH a couple times, but I didn't run that speed very long, and it only happened a couple times.

    Tom
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    gto1967gto1967 Member Posts: 1
    getting 35.5 mpg's on my '08 Cobalt travelling 350 miles per week, 90% highway.
    2.2 with the 5 speed. Highway speed kept at 68 mph.
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    tsjaytsjay Member Posts: 4,591
    Got 28.6 MPG last fill-up. I was doing my usual driving on this tank of gas, a mix of two lane rural roads and some in town driving.

    I guess there might still be some breaking-in of the engine to be done yet, since I have only 2700 miles on the car now.

    I plan to switch to Mobil 1 synthetic oil at the first oil change, and I believe that will give me an extra 5% on MPG. That's what switching to synthetic did for MPG on my 1994 Z-28 Camaro several years ago.

    I'm well pleased with that little Cobalt. It looks like buying that car was a good decision.

    Tom
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    occupant1occupant1 Member Posts: 412
    We have driven one full tank so far. Trip computer reports 29.7mpg. Actual fill for 388.0 miles with 12.435 gallons shows 31.2mpg. 70% highway @65-70, 20% city @ 30-40, 10% idling. AC on all the time. We will likely put 4-5 more tanks in during the next 5 days as my wife and I work.

    I LOVE the instantaneous fuel readout. I'll get up to speed and let off the gas as far as I can while maintaining highway speed and it'll creep up 32-33-34-35, etc. Changes in road surface (smooth concrete vs. rougher state highway pavement) make changes in the mileage. Drafting 2 seconds behind semi allows the mileage to creep up to 37-38. Coasting shows 99 most of the time but when it drops out of lockup around 35-40 it will drop to 80 or so as speed reduces. I leave the display on instantaneous all the time.

    I expect to average 32mpg for the whole rental. The last car we rented was a 2007 Corolla LE sedan and we took it to Houston and back from Fort Worth, averaged 35.6mpg for both tanks. I'm impressed more and more every time I drive a Cobalt and now that my wife has driven it some as well, she doesn't feel uncomfortable in a small car and it's back on our list. I wish they still had 4-cylinder Malibu sedans in the "e" fleet to "test drive" since we will likely be renting another small car for another week later in the month for another round of store visits.

    Our only other choices for a smaller car at the small local rental place we used were a 2008 Focus, a 2007 PT Cruiser, and a 2008 Kia Rio. They had larger cars (Impala, Lacrosse, new Malibu) and lots of trucks/SUVs/vans, too. I wish we could reserve specific makes and models.
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    gtodavegtodave Member Posts: 12
    6000 miles so far. 35.2 mpg. about 1000 miles with the mobile one oil change.
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    tsjaytsjay Member Posts: 4,591
    Filled up today and checked gas mileage, as I always do.

    I drove 284.1 miles on 9.602 gallons of gas for a 29.6 average MPG.

    Not bad!

    The car is up to about 3300 miles on the odometer now, so it is still most likely doing a little breaking-in.

    I think at about 5000 miles I might put some good old Mobil 1 in her.

    Tomster
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    tsjaytsjay Member Posts: 4,591
    Didn't drive as conservatively on this tank, but still got 28.9 MPG. Not bad.

    Tom
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    horsey55horsey55 Member Posts: 15
    I am currently travelling 300 miles per week, been averaging 37-38 MPG. 2.2 Automatic, 55-60 MPH on a two lane rural highway.
    I am more than pleased with this '08 LS Coupe. It has met my expectations and more as a commuter car that also has a fun to drive factor.
    Horsey
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    tsjaytsjay Member Posts: 4,591
    Horsey:

    WOW! Fantastic MPG you are getting! It really makes a difference when you slow down, huh? Guess you have the five speed manual tranny, right? I have the auto, so I don't have that nice overdrive 5th gear going for me like you have, if you have the five speed.

    You got it right about these puppies being fun to drive. That crazy little Cobalt of mine will actually push you back in the seat just a tiny bit during maximum acceleration. I would have never expected a car that gets the gas mileage that a Cobalt gets to have that much acceleration.

    I bought the Cobalt for bare bones economy, and I was about as excited over getting that car as I would have been over buying a new pair of underwear. It was the first time I had ever bought a vehicle that I wasn't infatuated with.

    Before long, I decided that I REALLY liked the looks of that little car, and I found the ride, handling, and acceleration, especially the acceleration, to be great. I like that car more the longer I own it.

    I can't believe that it only stickered for $15,530 and that GM had a $2000 rebate on it! I think the car is a SUPER value.

    Tom
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    horsey55horsey55 Member Posts: 15
    I have the Automatic in mine. I usually run Premium gas with no Ethanol,and that increases mileage a bit also.I know it is being burned more efficiently in the motor,as Ethanol makes my high compression Motorcycle motor run terrible.
    The $2,000 rebate was a big factor in this purchase as well, as I figured they would not have that offer for long. It was a good value.
    No problems at all so far with this car. I am very satisfied with it. It is nice to have a Forum like this to discuss the vehicle as well.
    Horsey
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    tsjaytsjay Member Posts: 4,591
    Horsey:

    How in the world are you getting that kind of gas mileage with the auto tranny? Is that 37-38 MPG what the DIC is showing, or is it actually calculated manually when you fill up the tank? I always manually calculate my mileage when I fill up.

    You said you drive only 55-60 MPH, and I know that helps, but I also drive similar speeds and don't come close to that kind of MPG. The last tank or two, I was not as MPG conscious and drove a little faster, but before then, the best MPG I could get was 29.5 for my usual driving conditions, i.e., mix of rural roads and in-town miles. I avoid jack rabbit starts, I let off the gas well ahead of red lights, so that I often don't have to come to a stop and go back up through the gears, and I try to hold a constant speed out on the highway and not be slowing down and speeding up all the time.

    Maybe my engine just isn't broken in good yet?

    It doesn't take many in-town miles to kill gas mileage, so maybe your driving is 100% rural, while mine is about 20% in-town.

    Tom

    EDIT:

    OK, I reread your first post, and I see that I missed the part about your car being an auto. Sorry.

    In your last post, I either missed the part about the Premium gas, or you edited your post to add that part.

    I have read tons of posts and read many articles that say that we should NOT use Premium gas in cars designed to run on 87 Octane. At best we are wasting money, and, at worst, we could be doing harm to the engine. I don't expect you to take my word for it, but please do some research on the subject. Might even be some discussions on it here in Edmunds.
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    horsey55horsey55 Member Posts: 15
    Tom,
    The high 30's MPG figure I used is under optimum conditions. Mix in some city driving, Interstate, etc., my figures are probably closer to what you are getting.
    Horsey
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    tsjaytsjay Member Posts: 4,591
    Horsey:

    Are those 37-38 readings from the "Instant MPG" mode on your DIC? I can get very similar numbers from holding a steady 60 MPH on level roads, but I have never come close to that range for an average for a whole tank.

    I'm enjoying this exchange of posts! Good to have some participation in here.

    Tom
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    okko1okko1 Member Posts: 327
    i have a ss/sc 06 model and my dic average this time year shows 30.5 mpg. and each time i manually check it is within 1-2 mpg of the dic. i drive mostly hi-way during the week and city on weekends. the speed limit is not a big consideration for me since i rarely drive it. the cobalt has put the fun back in driving for me. :shades:
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    horsey55horsey55 Member Posts: 15
    I use the Info on the DIC, but when I calculate the mileage it is quite close to the figure that is displayed. All the research I have done, including talking to mechanics that build race motors, is that Ethanol is not beneficial to internal combustion engines for various reasons including reduced burning qualities and the increased ability to attract moisture.
    Until recently, I was able to get 87 straight gas around here at a few stations. Not now though.
    Horsey
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    okko1okko1 Member Posts: 327
    you might consider a fuel conditioner. ethanol doesn't lubricate as well as gas.
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    gtodavegtodave Member Posts: 12
    i think i will try to find some of this for my oil changes from now on. it's supposed to be good for 15,000 miles.
    Mobil 1
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    tsjaytsjay Member Posts: 4,591
    The actual mileage calculated out to 28.9 MPG, and the DIC was showing 29.0 MPG.

    My usual driving mix. I'm pretty happy with that mileage.

    The car has a little over 4400 miles on it now, so it is probably still not quite broken-in.

    I think I will go with just a regular oil change at the dealership at 5000 miles, and then I might go to Mobil 1 5W-30 full synthetic at 10,000 miles. With 4400 miles on the car, the DIC says I still have 62% of my oil life left. If I went by the DIC for the oil change interval, I would be going over 11,000 miles before changing. No way I would wait that long, not even if I were using synthetic oil.

    Tom
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    tokyo_goddesstokyo_goddess Member Posts: 3
    Ok so my mom got me the cobalt in the summer of 05. I love it to pieces. But lately ive noticed that the computer dash says my mpg is really really low. Right now it says 19.6 MPG. When i first bought the car and filled up the tank it said i could go 250 miles w/o gas, now it says 200 or 210. Any other solutions as to why?

    I took it to firestone, they suggested new sparkplugs. Which i got and didnt necessarily needs. Then they checked for a leak in the fuel line/rod. Nothing. So then i took it to the dealership and they cleaned the air filter and said that may help. Other than that no one can tell me what if anything is wrong. Is it the computer? The dealership says they found nothing wrong.

    I'm thinking of putting a cold air intake in the car to help with the mpg issue, yeah it wont help alot, but it will help just that little bit. Help is much appreciated thanx.
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    cmhj2000cmhj2000 Member Posts: 381
    Cold air intake will do nothing to improve mileage. Some say when they put them on it did but I've yet to see it on either a dyno, in real life or with a scan guage.

    In my 35 years plus of pulling wrenches your solution might be as easy as running a fuel treatment solution. Many times the injectors will get dirty and that alone effects mileage.

    Not saying the above is the issues, just the most common one I've seen if there are no codes or problems seen by your dealer.

    Tire/wheel alignment, tire pressures, transmission fluid and I could go on and on can in time all cause fuel issues.

    There are a slug of fuel treatments on the market. Amsoil has the best.
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    tokyo_goddesstokyo_goddess Member Posts: 3
    i feel like ive covered everything that may affect the mpg. The tires were changed, there was a new wheel alignment. I just think something drastic has to be affecting the mpg. Last month it was 21 mpg now its 19. somethings up...
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    cmhj2000cmhj2000 Member Posts: 381
    Different tires can make a big difference either way.

    Has this mileage change been a sudden issue or gradual? If gradual then my first suggestion is where I'd start.

    Without being able to see, drive and scan your vehicle there are a lot of unknowns for me.
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    okko1okko1 Member Posts: 327
    if the dealership provides the mobil 1 it will cost you about 9.00 bucks a court :shades:
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    tsjaytsjay Member Posts: 4,591
    My dealership changes the oil and filter for $10 when you bring your own oil and your own filter.

    Tom
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    tokyo_goddesstokyo_goddess Member Posts: 3
    this is relatively sudden, within the past 2 months ive noticed the gas was getting smaller. But it may have been gradual for all i know >.>;
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    cmhj2000cmhj2000 Member Posts: 381
    So you really don't know. Rather than playing guessing games as I said, the reasons are vast. Try my original suggestion, then see what if any difference is made.

    https://www.amsoil.com/storefront/api.aspx?zo=1473695

    If anything it should be done once or twice a year anyway.
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    harrisblackharrisblack Member Posts: 28
    Maybe its the driver.
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    tsjaytsjay Member Posts: 4,591
    As someone else asked you, have you actually checked the gas mileage manually, or are you simply going by the indicated mileage on the DIC?

    You should check the mileage manually before you do anything else.

    If the car has really dropped to the kind of mileage you are seeing on the DIC, then it should be running rough, or it should have gotten extremely sluggish on acceleration, or both. If it seem to run as smooth as ever and has the same acceleration that it has always had, then I strongly suspect that you are getting a false low mileage reading on the DIC for some reason.

    Check your mileage manually and let us know what you get, OK?

    Oh, how many miles on the car, and what are your driving conditions? Have your driving conditions changed since the days when you were getting hight MPG?

    Tom
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    tsjaytsjay Member Posts: 4,591
    Man, those are sure SMALL filters on the Ecotec engines, huh? I'm not sure I would feel very safe going more than 5K on those puppies. I had thought about switching to Mobil 1 at 10K miles and then going 10K between changes. If I did, I might want to change the filter at 5K.

    I guess there might be just as much paper in these filters as in some of the small spin-ons. We just don't see how little paper is in the spin-ons, because of the can.

    Tom
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    tsjaytsjay Member Posts: 4,591
    The DIC was showing 29.1 MPG average for this tank of gas, but the manual calculation worked out to 28.2 MPG.

    It looks like I am going to be able to count on getting 28.0 to 29.5 MPG on my normal mix of driving.

    Considering that my mix is 15% to 20% in-town driving, and none of it is Interstate or Parkway driving, I am pretty happy with the mileage I am getting.

    Tom
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    dispencer2dispencer2 Member Posts: 299
    On the first tank in town I averaged 23.2. I'll take it to Dallas in November -400 miles - and we can see what it does on the road.
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    tsjaytsjay Member Posts: 4,591
    I have never run out a tank of gas with all city driving, but that 23.2 doesn't sound too bad for all city. The EPA estimate is 22 MPG for city, right?

    Are you happy with that mileage?

    Tom
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    fillbackautofillbackauto Member Posts: 1
    link title
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    dispencer2dispencer2 Member Posts: 299
    I assume that it will improve when it gets broken in. Compared to a 1999 Century (17) and my 2003 DeVille (15) it is great. The best thing about the car (compared to Toyotas and other Japanese compacts) is the ride. I don't see much difference from the 2006 Impala I had. Obviously there is no comparison with the Cadillac but for a small car it rides very well. Toyotas are stiff and uncomfortable at least for me. The Yaris is horrible -the front seat doesn't go back far enough. The Chevrolet HHR isn't much better. Very small-feeling and cramped.
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    dispencer2dispencer2 Member Posts: 299
    Actually -"city" out here (Clovis NM) isn't really city bumper to bumper driving like I had for years in Washington DC. When we were in Kauai in January with a 2008 Cobalt rental car we averaged about 28 in road (50 mph maximum) and small town driving. Around here we probably average about 20 mph with city streets, some stop lights, stop signs etc. It would be like suburban driving elsewhere.
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    tsjaytsjay Member Posts: 4,591
    I got 28.8 MPG on my last fill-up for my regular driving.

    Tom
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    tsjaytsjay Member Posts: 4,591
    I took a 265 mile (each way) trip yesterday and checked gas mileage. The pump failed to shut off automatically when I filled up on the other end of the trip, and a good amount of gas overflowed before I could get back over to the nozzle and shut it off. I was on the other side of the car getting ready to clean the windshield when I heard the splashing noise. The last time I made the same trip, I averaged 33.7 MPG.

    I did a little experiment as I drove across I 64 in southern Illinois between the Wabash River and Mt. Vernon. I reset the average MPG on the DIC and drove a steady 70 MPG for 15 miles, and the MPG reading was 32.7 at the end of those miles. I reset it again and drove a steady 60 MPH for about ten miles (had to stop at a rest area) and got 37.5 for an average MPG for those miles.

    Tom
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    powderkeggpowderkegg Member Posts: 22
    I have an 08 Cobalt coupe XFE. The car has 4500 miles on it and the mileage has been about the same for me since mile 1. I get about 30 City and 38 Highway. I got 42 on an 90 mile trip but only once. Most of my driving is mixed so I generally get 34 tank to tank. I calculate mileage manually and use the DIC and find that my calculation is ususally within 0.5 mpg but the DIC has displayed as much as 3 mpg lower. Probably due to where I stopped when I fill.

    Ben
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    grosloupgrosloup Member Posts: 239
    That's right!

    Your DIC reading is always based on your last hour of driving. So if you did lots of "stop and go" during that last hours it goes down.
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    tsjaytsjay Member Posts: 4,591
    "That's right!

    Your DIC reading is always based on your last hour of driving. So if you did lots of "stop and go" during that last hours it goes down."

    I didn't know that! That's good to know, but I would prefer that it just kept averaging from the last time it was reset.

    Thanks.

    Tom
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    horsey55horsey55 Member Posts: 15
    Well I guess my 38 MPG that I was getting earlier is confirmed.....
    Horsey :-)
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    tsjaytsjay Member Posts: 4,591
    I can see that it would be possible to average 38 MPG on strictly highway driving, with the speed held to around 60 MPH, which is pretty much what you said your typical driving conditions are.

    You should be a happy camper to be getting that kind of mileage.

    I have to admit that it was a little hard to believe at first. :)

    Tomster
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