Chevrolet Malibu Maxx Real World MPG

bimmerboy750bimmerboy750 Member Posts: 4
edited October 2014 in Chevrolet
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 Member 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).
  • bimmerboy750bimmerboy750 Member Posts: 4
    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.
  • bimmerboy750bimmerboy750 Member Posts: 4
    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 Member 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....
  • bimmerboy750bimmerboy750 Member Posts: 4
    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 Member 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.
  • kurtamaxxxguykurtamaxxxguy Member Posts: 1,798
    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 Member Posts: 236
    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.
  • hgr3inokhgr3inok Member Posts: 28
    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.
  • kurtamaxxxguykurtamaxxxguy Member Posts: 1,798
    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?
  • kansasronkansasron Member Posts: 3
    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.
  • kurtamaxxxguykurtamaxxxguy Member Posts: 1,798
    ...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 Member 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 Member 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 Member Posts: 399
    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 Member 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 Member 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 Member Posts: 399
    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 Member 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 Member 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.
  • maxximus_edmaxximus_ed Member Posts: 6
    I also am a little disappointed in the mileage I get with my 07 maxx although to be honest it is also dependent on my driving habits. Speeding along on relatively flat highways at 120kmph the computer shows about 9.8 to 11 liters per 100km. When I slow down to about 110-112kmph it drops to 7.2 to 7.6 liters per 100km. I have informed my wife that trips out to the east coast will now take an extra 1 or 2 hours. What bugs me though is that the car I traded in, a 2000 Impala LS with a 3.8 liter motor would show typically 7.5 to 8.5 liters per 100km at 120kmph. The higher milage ratings of the maxx was one of the selling points to my wife.
  • slringeslringe Member Posts: 1
    My 05 Impala also got better gas mpg then my 05 Malibu Maxx. I get 19.8 to 22 in the city. Seems like I am always filling her up. Highway it does get better about 28-30. Is there anything I can do to get better mpg? I checked the air cleaner, it was clean.
  • highmiler650highmiler650 Member Posts: 75
    IMHO the two most effective ways of saving gas are to make only long trips and to flow with the traffic. Don't try to be the first at the next red light and try, within reason, to use the brakes as little as possible.

    All the energy destroyed by braking you will have to make up using gas.

    My brief experience with rental Impalas showed me that with a light foot it is possible to achieve 30 MPG in mixed traffic (50% highway, not more than 65 MPH, 50% city, stop and go).
  • cpinkhamcpinkham Member Posts: 7
    Hi all, we continue to be amazed by our '06 Maxx fuel economy. We are getting 30 MPG (measured by amount of gas taken at refuel divided by miles travelled) on I-95, with and without AC running. The computer display shows 31, so it's pretty close. We have an LTZ with the 17" wheels. We keep tires inflated, car tuned, etc.; and drive gently. Around town we average 24. Pretty darn good for a big car with V6 and automatic trans.!
  • kurtamaxxxguykurtamaxxxguy Member Posts: 1,798
    Before I forget, the '04 Malibu Maxx LS I used to drive up here in Portland managed to get around 26 - 28 mpg on the freeway, but only 18-19 mpg in the hills of Bull Mountain (a series of 500' high hills which force cars up and down up to 30 degree slopes).

    I've seen several Maxxes up here. The snow required a change to a Subaru. ;)
  • ssanssan Member Posts: 5
    I own a 07 Maxx In Buffalo NY, it has never achieved the 20+ mpg that everyone claimes. We have owned it since new... As of recently with the 10% ethanol blend we (my wife and I) have noticed the mileage dropping as low as 14 mpg!!! Granted this is around town with the AC on etc. On a road trip to Florida we avg about 22 mpg on the highway... the car only has 35k miles and yes the tires are the correct size, new air filter etc... not sure if anyone else has heard of any other malibus like this or can help? Thanks..
  • comem47comem47 Member Posts: 399
    My wife has an '06 V6 Malibu and was initially getting 29- 30 on her daily commute to Rochester from the burbs (about 25 miles mostly 490). She changed jobs a few years ago and now it's mostly back roads with a mix of driving and she still gets better than 24-25. Something is indeed wrong. (The only time she sinks to 20 is in the winter with warming up the car with the remote and stop and go), It might be worth the $ to have a Chevy dealer put it on an analyzer.
  • ssanssan Member Posts: 5
    This is what I have been told by many after some back and forth with the dealer trying to plead my case it is going in next week lets hope something shows up...
  • ssanssan Member Posts: 5
    Well nothing is going on that would show up the dealer said they next step would be to pull the plugs clean and regap them. Also a possible fuel system cleaning. This all sounds great for a minimum of 300 bucks... the car does have 35k miles on it but the fact still remains that after 35k miles a car really should not be going through an issue like this. I have run a few tanks of fuel system cleaner through it no big gains there so I am not sure what else the dealer will do that will make big gains to see the mid 20's that this car should get. Also If the plugs should only be replaced after 100k miles has anyone else had to clean and regap them by 35k?
  • comem47comem47 Member Posts: 399
    Sorry to hear nothing found yet. My wife has just over 50K on her original plugs.
    (I'm assuming they are iridium, like my Mitsubishi is in order to get 100K (both V6s have hard to reach plugs on the firewall bank, so it pays to use iridiums to service less.). I'm surprised the analyzer could tell the plugs were firing correctly with the pulse display. How's the power ? (I know clogged catalytics can hurt both mileage and performance)
  • ssanssan Member Posts: 5
    The power is the same as it always been since new which seems fine so as a basis for comparison I would say that that is not the problem. Dealer said everything came back to spec and now they would pursue the plugs like I had mentioned... after that they seemed to be reaching for a solution...I am reaching as well I realize we do mostly around town driving but in Buffalo NY traffic is never "real' bad. Our other vehicle is a v6 explorer and even that gets 14-16 around town so for the malibu to be getting similar something is off.. Dealer also checked for computer updates etc. Just not sure I want to start spending hundreds of dollars for experimental fixes. On the other hand I would like to solve the problem but at this point solutions seem vast and many!
  • comem47comem47 Member Posts: 399
    edited August 2010
    I guess I'm out of ideas on this. If you've stuck with stock tires( no reason for odometer difference) and the analyzer came up clear I don't know unless you're a severe lead foot driver. (I know I am compared to my wife, but not that big a difference) Hope you find it as we've always bragged to our friends about how good her Maxx is for an auto V6 when it comes to MPG.(she's got the power when she needs it with no apparent sacrifice in MPG). I don't think they made any big changes in '07 vs the '06 3.5L engine. I would have thought their tests would have revealed stuff like a stuck choke with all the things the computer measures.
  • marks_maxxmarks_maxx Member Posts: 1
    I recently bought a 2006 Malibu Maxx with 41,000 miles. Yesterday I did some freeway traveling and was pleasantly surprised when my mileage per the DIC read over 32 miles per gallon for the trip. The route included hills, flats and some traffic so the mileage is a good representation of expected future freeway mileage. When I bought the car the DIC read 24 mpg and this is most likely the combined mileage the car gets. :)
  • malexbumalexbu Member Posts: 169
    I love my 2006 Maxx but the DIC number is about 2 MPG better than the reality. Record fuel purchased and the distance between the fillups, divide the latter by the former -- you'll get your numbers and tnen we can compare them with mine. :-)
  • sgr5516sgr5516 Member Posts: 159
    I had 2004 Maxx LS. Averaged 24-25 MPG mixed driving (calculated by me). Also, could go 5-6000 miles between oil changes per Oil Life Monitor. That car was totalled around 30,000 mi (no injuries). I replaced with 2006 Maxx LTZ, which has same engine, trans, steering as the 2004. The 2006 lifetime MPG to-date is only 20.4 (calculated) and oil needs to be changed every 3000 mi per OLM. DIC on both overated MPG by 2.0 mi.
  • malexbumalexbu Member Posts: 169
    Your data on the 2006 is close to mine 2006 LT: 2 MPG DIC overrating, OLM readings equivalent to about 3500 - 4000 miles between oil changes, recent (this sping and summer) real MPGs being 22-24, at the average speeds recorded from 24 to 42 MPH.
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