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Chevrolet Malibu Maxx Real World MPG

Got an 05 MAXX that I enjoy. I was getting a rock steady 27 MPG average driving in the D.C. area daily. I've accumulated 14,000 miles so far. Mileage has been a plus... up till now.

A month ago, I lost my dashboard power, HVAC controls, and radio. It wasn't a fuse, but a bad 3controller unit. The controller had to get replaced... under warranty.

At the same time, gas prices surged from $2.65/gal to $3.05/gal and I also understand that we are swtiching over to E-10 fuel (10% Ethanol).

Well, since I got my car out of the shop, my MPG has dropped greatly from 27 MPG to 22 MPG.

What happened? The repair, E-10 switchover, or both?


  • e2helpere2helper Posts: 1,002
    You dropped almost 20%. There was a study released last year, maybe biased ;) , from the American Coalition for Ethanol that averaged only a 1.5% drop in MPG with E-10. You can find it with simple Google search

    Are your MPG numbers based on your own calculations or from DIC??

    If the module replaced in vehicle was one that does the MPG calculation then it is possible that you are just seeing the effect of some initial lower MPG driving and after a while your average might get back to where it was.

    There is another potential - in the past folks have posted that the DIC display for MPG was a bit optimistic. There might be a potential that the calibration was updated (but that wouldn't explain that big of a jump).
  • I read those figures from the E-10 site earlier. I;ve also read about observed MPG reductions as high as 25%! What am I gonna believe? Probably my wallet.

    The MPGs quoted are from from DIC. I reset the MPG about every 60 days. It always converged on 27 MPG. I suspected module replacement and shop time (running engine at idle for extended times, short test drives) would have had an impact too. MPG from the DIC coming out of the shop was around 10 MPG. I drove it without resetting it for about a month and it converged on 22.3 MPG. I reset it yesterday. Looks like it's converging on 22 again. I have some 5 mile stretches of highway driving and it appears that the MPG is not getting above 27 MPG on those intervals!

    I drive 75 miles a day, 5 days a week (375/wk) (I don't keep track of the trip odo).
    What I need to do now is go through my gas receipts over several months (I keep 3 months of receipts) and see if I can recount the gallons consumed in the 2 months before repair and the one month afterward. I should've been putting in about 14 gal / wk. giving me about 26.8 MPG measured at the pump before the repair. Now I may be filling up no more than every 6 days or 16+ gal/wk.

    I'll report back on findings. If this is happening due to E-10, then people need to know.
  • I am still tracking this issue, but I think I found a smoking gun.

    MY other vehicle gets 24+ MPG highway. That has been rock steady for years up until recently. This weekend, I reset its MPG display for a long highway trip. My best average has also fallen to 20 MPG!

    Two vehicles (one GM one Dodge) both experience about a 20% loss in fuel economy. What's going on here?

    I'm curious to hear from other Maryland drivers.
  • paopao Posts: 1,867
    I burn E-10 here in northern va....and do about the same drive.....Im getting about 375-400 miles per tank in the highway/city driving.......I do 75 mile round trip a day...mostly toll road, 495, to Alexandria....I dont notice an appreciable difference in my Maxx....67K on mine....all OEM and no warranty work or updates....

    just filled up on Monday with just over 300 miles on the trip odometer....DIC showed 27.4 MPG and average spd of 43 MPH, I reset it at every fill up....experienced shows me the DIC is 1.5-2.0 MPG off in the calculation.... and still had a 1/4 tank at fill up....
  • My average now (shown on DIC) is up to 24.3. That's an improvement (without doing anything different). but still off from the 26.7, now about a 10% difference. If could find some whole 87 octane (no ethanol or MTBE), I could do a fill-up and drive comparison.
  • maxxindmaxxind Posts: 22
    A gallon of ethanol has about 2/3 the energy content of a gallon of gasoline. So, if you are getting E-10 (10 percent ethanol), you are buying about 96.5 percent of the energy that you'd get with a gallon of straight gasoline.

    Given that, if you are getting 29 mpg on ethanol, you'd probably get about 30 mpg on straight gasoline.

    I have an '05 Maxx and try to run it on straight gasoline unless I'm somewhere that it's not available. I do notice a drop in MPG on ethanol-blended gas, but the specific amount is hard to say because so many different factors affect mileage. Overall I average a little over 30 mpg in my Maxx, and that's about 80 percent highway and 20 percent city. I try to drive at a reasonable speed on the highway. Fast interstate driving (75-80 mph) pulls the mileage down to about 28 mpg.

    Has anyone ever noticed how the DIC always displays certain mileage figures, like 28.7, 29.4, 30.2, 31.8, 32.7, etc.? (Except for right after you reset it, when numbers can be different from those.) I think it does that because it actually calculates mileage in metric terms (liters per 100 km), rounded to the even decimal place and then converts it back to the English system.
  • Anybody out there have some feedback on the '07's for mileage?

    The MPG this year was rated lower, but that may be due to changes in how MPG's now being calculated.

    As for my '04 maxx, it's pretty consistant with around 24-26 for mixed highway/city driving.
  • mr_botsmr_bots Posts: 225
    It is possible that the new engine doesn't do as well with the extra weight and taller gearing of the Maxx as the old LX9. That mixed with altered EPA guidelines and then the extra load of a p/s pump on the 07 models probably accounts for the decreased mileage.
  • Our 2004 LS (purchased new in January 2005) turned 22,000 miles as we completed our 2,500 mile road trip from Norman, OK, to Mount Rushmore last week. We averaged right at 28mpg (manually calculated) with a lot of 75mph+ and some stop-and-go for scenic turnouts. The car performed flawlessly.
  • Am curious how the 2007's are doing...

    Also, one web source claimed the LZ9 engine the SS version is using has, for 2007, active fuel management.

    I've not seen that in any '07 Malibu literature. Do the '07 SS's actually have this?
  • Just picked up my 2006 LTZ Maxx Friday. Yesterday drove 190 miles in heavy winds (unfortunately no tail wind) and averaged 27.9 MPG, which I was very pleased with.
  • ...was that the SS Impala with the V8 engine was rated at 18 mpg City, ..vs.. the Malibu Maxx SS rated at 17 Mpg for the city. There were similar differences for Highway mileage.

    We have a small block 305 HP V8 here getting better mileage than a 240 HP V6. I'm frankly amazed how bad the Maxx SS mileage '04 Maxx LS averages 24-26 mpg in mixed driving.
  • milo2244milo2244 Posts: 3
    I get around 27 on the highway and low 20's in town...with 75 percent highway and 25 percent town I get about 24 mpg...I was a little disapointed. I'm hoping once the weather warms up here in WI my gas mileage will improve.
  • paopao Posts: 1,867
    04 Maxx LT here with over 120K on it..still averaging 26 city and 30-32 highway depending on hills and speed.....
  • comem47comem47 Posts: 390
    I wonder when the cars are tested for fuel economy whether E10 ethanol blend is mandated. (we can't get other than that in NY and I know mileage would increase with straight gas). While it would be nice to be less dependent on foreign oil the more I read about E10 ethanol blend the less I like it (gas separating into layers if allowed to sit too long...more of a problem with lawn mowers, etc that sit a while and especially a problem in boats, being near water, or anything not using fuel injection). Also reading that the ethanol is added later in the manufacture and there is room for fraud/error so everyone's mileage could vary if say the 10% is exceeded -which is highly illegal as engines can be damaged).
  • icemanmuicemanmu Posts: 2
    So everyone's reporting high 20s....
    Why am I only averaging 20 on the in dash computer?
    I don't drive heavy and the tires are inflated properly.
    Just bought my 07 maxx in October and still haven't seen these mid 20 figures.
    Any idea why my efficiency would be so low? :sick:
  • paopao Posts: 1,867
    I have an 04 Maxx, averaging 24-26 in the city......and getting 30-31 on the hwy with my V-6....but the later malibus did have an engine change...with a slightly higher output....still 20 seems a bit low........
  • comem47comem47 Posts: 390
    So everyone's reporting high 20s....
    Why am I only averaging 20 on the in dash computer?
    I don't drive heavy and the tires are inflated properly.
    Just bought my 07 maxx in October and still haven't seen these mid 20 figures.
    Any idea why my efficiency would be so low?

    I assume this is a leftover 2007 you bought new (OEM tires)? Otherwise verify the tires are the correct size. Also verify real mileage vs the "computer" mileage by actually figuring out yourself the fillup gallons over a tankful. Even I, (Mr. Leadfoot) get high 20's when driving my wifes 2006 in combined driving. She's right on the threshold of 30 now and should go up with warmer weather. Other than that I wonder about injectors or re-flashing CPU (try under Warranty). Where do you buy gas? You should do fine with the 3.5L V6 (if you got the 3.9L SS then I could see the lower 20s)
  • hickorychickoryc Posts: 25
    Up through 49,000 I averaged 28mpg. Added a red bottle of STP gas treatment. Next 6 tanks, averaged 30. Today's fillup at Sam's Club was 30.94.
    Also tried STP with the Expedition (5.4) and removed luggage rack cross bars. First fillup: 16.7. That might be 1 mpg improvement over average. Gotta believe STP is giving me 2 mpg in the Maxx (1 bottle every 6 tanks of gas). This translates to about 25 more miles driven on the same amount of fuel per tankful. My impression is that the engine is running more smoothly as well. One more note: Running 36 pounds in all 4 tires, which have maximum inflation rating of 51. Ride is smooth. :)
  • icemanmuicemanmu Posts: 2
    It's a 3.5 liter.
    OEM tires, yes. Inflated to 32 all around. (reccomended by dealer, door says 30).
    I was thinking about flashing the CPU as well, or maybe hooking it up to the programmer to see if everything looks right. Highway I'm getting (as the computer says) the advertised 30, which I'm happy with, but combined it still reads 20...
    I'll try filling it, reset trip, calculate it out that way and see what's really going on. It may just be I too am "mr. leadfoot", but my Monte Carlo didn't see the same number of fills as the malibu does... odd.

    I buy gas at Irving.
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