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Chevrolet Malibu MPG-Real World Numbers

145791016

Comments

  • csandstecsandste Posts: 1,866
    Although I haven't noticed much improvement in mileage after break in with GM engines, HyunKia engines are very tight when new and improve steadily in MPG for at least 10-15000 miles.

    36 lb. gives better gas mileage than 32 in most cars with no problems with increased tire wear.
  • packer3packer3 Posts: 277
    keep in mind 36 lbs goes higher in the heat, one thing you never want to do is to push the tires limitations
  • hickorychickoryc Posts: 25
    My '04 Maxx did not get over 30 MPG on highway until 50,000 miles. Now at 60,000, it has averaged 33 on the highway and 28 mixed. Wife's '08 Civic has been inching up in the MPG category each fillup from 32 to 37. I fully expect it to increase even more. To qualify the statement regarding the Maxx, I previously posted that I added STP (Red can) for the first time at 50,000. On a side note, in June we fully loaded the Maxx for vacation and it still got 33 highway miles out of every gallon, about the same as my solo daily commute.
  • malexbumalexbu Posts: 169
    Two long trips this year (a college parent's duties), in the 2005 Malibu Base Sedan (MPG computed as distance/fuel, the distance one way about 1150 miles):

    +----------+------- +--------+
    | Where | Whn | MPG |
    +----------+-------+---------+
    | MA-TN | May | 36.64 |
    | TN-MA | May | 36.78 |
    +----------+-------+---------+
    | MA-TN | Aug | 36.55 |
    | TN-MA | Aug | 37.37 |
    +----------+-------+---------+
  • I'm looking for some information on a specific model. I'm seriously considering the 09 LTZ with the 4 cyl and 6 speed automatic. It's rated at 22 city and 33 highway, but I'd like to get some real world input. I've gone back through several pages and seen only one post on this particular car. The 08 similarly equipped or a 2LT with the same drivetrain would be OK too, since it is the same car.
    My driving style is somewhat aggressive. I drive 5- 10 over. I don't over-inflate my tires (whatever it recommends in the manual is what I go with). I get away from stop lights quickly (I hate people who dawdle when there's a string of traffic trying to get through a short green light). I come up to speed quickly when entering the freeway. My commute starts in suburban traffic (2 - 3 miles with lots of lights), then about 25 miles of freeway (65 -75 mph) followed by another 5 miles or so of suburban traffic with several lights (40-45 mph, when it's moving).
    I really like this car, but I'm also considering a small CUV (Subaru Forester Limited) for the AWD and utility it offers. I've been following that thread pretty closely and it appears that I could reasonably expect to average about 23 - 25 mpg. I'd like to know that I can do significantly better with the Bu, if I'm giving up the AWD and utility.
    So any input would be appreciated.
  • We took delivery of a 08 Malibu LTZ 4 cyl 6AT on 8-23-08 with 360 miles at delivery.

    On the first tank with a lot of idling to figure out onstar and play with all the functions, we averaged 28.3 with an average speed of 38 mph. Tire pressure is at recommended 30 PSI. My wife is driving the car and has a heavy foot. Her commute is about 2 miles of stop and go followed by 16 miles of highway(65-80mph) and then another 2 miles of stop and go. She uses no fuel saving techniques.

    So far on the second tank we are averaging 28.8 with an average speed of 39 MPH. On this tank I drove on hilly/curvy country highways for about 90 miles and the readout was at 32.5 mpg and climbing when we got home. I checked instant mpg at 60 mph with the cruise set on a level road and very little wind and it was between 43 and 46 mpg, I think the car will easily get the advertised 32 mpg highway.

    On the first fill we had 14.4 gallons and 413 miles for an actual average of 28.68, so a little better than the readout calculated. So overall the readout appears pretty accurate so far.

    We really like the car so far, it is comfortable, rides and drives very nice and is quiet inside.
  • That was very helpful! That's just the sort of information I was looking for and is very encouraging. :shades:
    I have been vacillating between the Malibu and a small SUV ('09 Forester). The SUV offers more utility and AWD. It doesn't do too badly on mileage (~25 mpg). But it looks like the Malibu will do quite a bit better, plus it offers a few more creature comforts in LTZ guise. Plus, I know the Chevy dealer and they're close-by.
  • kam327kam327 Posts: 115
    Rented a '08 Malibu 1LT with 4 Cylinder and 4-speed auto during a visit to Florida this weekend. I topped off the tank, ran a round trip between Tampa and Naples, and when I refilled the tank I calculated 28 mpg. That's 2 less than the EPA rating. It's puzzling since it was 99% highway driving. I was doing about 75-80 and noticed the RPMs were around 2800 which seems high. Maybe you have to do 65 or less to get 30mpg? If you do 65 on I-75 in Florida you'll get mowed down by pickup trucks.
  • It probably has to do with 2 things.
    First and foremost, your rental has a 4 speed automatic. The 2LT and LTZ are now available with the 6 speed automatic. I'm guessing the addition of 2 more gears makes a significant difference.
    Second, while I, myself, have a heavy foot and have been known (frequently) to drive those speeds, the EPA test does not. I suspect if you slowed down to 65 - 70, you might gain 1 to 2 mpg.
    With a 2.4L 4 cyl and a 4 speed automatic, 2800 rpm at those speeds is probably not out of line. Our VW 1.9L diesel with a 5 speed manual churns nearly that hard at those speeds.
    FWIW, a bigger engine with a couple more gears will do about as well. My 2003 Corvette with the 5.7L V8 and 6 speed manual would have returned 28 mpg on the trip you described. But, of course, it has enough power and is light enough that it is hardly turning at those speeds. Having said that, I once rented a Buick LeSabre with the 3.8L V6 and 4 speed auto. I drove it from Indianapolis to KC at about 75 mph and it returned right about 28 mpg. So smaller doesn't always equal more economical.
  • kam327kam327 Posts: 115
    What surprised me was that it was quite a bit lower than the EPA rating of 30. I can get the EPA highway rating in my Mazda Tribute driving around 75-80 but if I slow to 65-70 I have gotten 3-4 mpg over the EPA rating. I was expecting the same of the Malibu but I guess all cars are different. The lesson here is that you really have to work hard in the Malibu to get the EPA highway rating. I would expect now that with the 6-speed transmission you may get 30-31 on the highway whereas the EPA rating is 33 for '09.
  • My wife has traveled a total 87,123 miles since 2003. She has used 3,120.577 gallon of gas = 27.919 MPG. This is with a 3.5 V-6 Malibu
    Yes we have synthetic oil 0W-30 with once per year oil changes.
    Ken
  • I took the plunge and bought the Malibu yesterday. '09 LTZ, 4 cyl 6AT, granite black over cocoa/cashmere. I'll let you know how I do after I've had the chance to run a few tanks through it. Right now, I'm averaging about 24 mpg on this tank. Some around town, some freeway. I hoping for a something better.
  • hjr3hjr3 Posts: 2
    What's the MPG everyone is realizing on the 6 cyl/6 speed auto Malibu? And, at what speeds?

    Thanks
  • Conditions: daily drive, ~25 miles of I40 between Old Fort NC to Asheville NC, speeds between 55-65, ~5 miles rural route, speeds between 30 and 55, and between 1 and 8 miles in downtown Asheville, all 1 way. Around 5 to 6 miles of the I40 drive is on Old Fort Mtn, steep grade. Granted, on the way home that stretch is all downhill, but it's the opposite on the way to work. The rest of the I40 slog is mostly slight uphill / downhill between Asheville and Black Mountain.

    Now to my numbers- driven in these (nearly ideal? I always thought flat terrain would be better, but..) conditions, I have been getting anywhere from 28 to 32 mpg, with the overall sitting right at 29. The overall includes the initial break-in of 500 miles where I stayed off the interstate as much as possible (more stop'n'go), kept speeds below 55 where I could, etc.

    I have noticed while driving around strictly in downtown Asheville that the reading varies between 16's and 22, with the lighter traffic usually being higher, but lots of stop'n'go / accelerating against the hills being closer to 17. Speed zones anywhere from 35 to 50 mph, though sometimes barely getting up to speed before stopping again.

    Those are my observations. Let me know if there is anything more specific you want to know.
  • Bought my new Malibu 2008 2LT, 4 cyl engine, last week from CarMax. It is almost brand new and has only 1600 miles on it. The DIC currently shows 21.6 mpg for my last 400 miles driving. I drive about 25 miles one way to work, which has about 60 % City/40% Highway.

    I have been scared to notice the fuel gauge moving down quickly while driving it on highway. I never experienced something like that. I own a honda Civic 96 and Sienna 04, and have never seen the fuel gauge noticeably moving while driving these cars. My Sienna Van has 6 cyls with 54K miles on it and still average 20.5 mpg.

    I researched this car for the last 4 months and saw many praises on its fuel economy. But I did not expect it this bad. I was hoping for 26-27 mpg average.

    When I bought the Malibu, I wondered why the last owner would resell the car after just couple of weeks driving it. I remembered to see 16.7mpg when resetting the DIC. I guess that might be the reason he dumped the car to carmax.

    Now I am wondering I would do the same. I will start measuring the gas manually tomorrow to see exactly what mpg I got.
  • In my opinion/advice. Don't give up yet. Here are somethings I do to increase my MPG and maybe it can help you. I don't drive a Malibu, but this might be helpful.

    1. Roll to Stop's and Red Lights. Anticipate and judge beforehand and let off the gas pedal and roll to stop.

    2. Use as much cruise control as you can. For example whenever you have long strecthes of a certain speed limit cruise control it.

    3. Find the speed where you engine hits its last gear. In other words if you have a 4 speed automatic, try to feel at what MPH its goes into 4th and engine enters smooth rpm. What I am getting at is try to get to your highest gear as soon as possible. Obviously obey speed limit as all times.

    High RPM's kill the MPG of a car. Hope this helps. The Malibu is a nice car and you should achieve good MPG.
  • bryanbryan Posts: 217
    I too have a 2LT with the 4cyl and 4-speed transmission--now have 2500 miles since May delievery. Each tank the mileage is creeping up--first tank got right at 31 on the highway; I'm now getting 34 making the same trip each weekend. Your mileage should improve as you rack up more miles. I also have an '07 Malibu LS, and routinely get 36 plus on the highway!

    Good luck and keep us posted as you too rack up more miles.
  • I can sympathize. I just bought a new '09 LTZ with the 4 cyl and 6 speed automatic. I've been driving a combination of suburban and freeway with the majority being the latter. I don't take any great pains to increase my mileage, nor do I care to; I just drive normally. I flogged our old Beetle and got 40+ mpg (it was a TDI).
    The end result is, my first tank was under 24 mpg (23.7 or 23.9, depending on whether you believe the DIC or the calculator). My second tank was just under 26 mpg. My current tank is under 25 mpg. I too have been alarmed at the rate the needle on the fuel gauge drops. I truly expected better. Had I known this was what I could expect, I'd have purchased the Forester for the additional utility and AWD the mini-SUV provides. It's fuel mileage is about that good. I have a list of niggling complaints about the Malibu, but this is the biggest.
  • I have been reading these posts for some time now while shopping for a car. I was trying to decide between the 3.6 and 2.4 both with 6speed transmissions. I started looking at the Malibu but both me an my wife like the Saturn Aura better. Tonight we took a test drive in two Aura XR's with each engine. The purpose of the drive was to travel the same route and compare the MPG after driving as efficiently as possible. The route included a short stretch of highway (3/4 mile) having a couple of traffic lights and about 5 miles of hilly urban 6 lane highway with light traffic. The average speed was 45 to 50 MPH on the highway portion. The 2008 3.6 had 5,000 miles on it and returned 28.2 miles per gallon. The 2009 2.4 had 1,000 miles on it and returned 30.6 miles per gallon. The 2.4 was at 31.7 when I caught a light on an uphill grade and had to reaccelerate up the hill to get back to my starting point.

    It is true that the mileage improves on these engines after break in. I would run regular oil during the first 10,000 miles to be sure that it is broken in then maybe switch to synthetic oil.

    I wanted the 2.4 which performed very well, my wife wanted the 3.6 because she liked the dual exhaust look and color better. I liked the 2.4's 17" wheels and she liked the 3.6's 18" wheels better. I felt that the 2.4 could easily achieve over 33 MPG on level highway.

    The sales manager that drove the 3.6 told me that he put the 5,000 miles on the demo mostly driving from Pittsburgh to New Jersey and that he would get 33 MPG going to NJ and 29 MPG on the return trip.

    These numbers are from the on board computers and were not hand verified. In any case I lost and we ended up buying the 3.6 Aura. I tried to sway my wife by telling her that we will be owning this car for 8 years or more and who knows how high gas will be by then. But she was not to be deterred. I know that the 3.6 will tease me to drive faster and will result in lesser mileage if I succumb. At least we both agreed that we liked the Aura.

    I fully expect that the 2.4 has the ability to return 6 more mpg's than the 3.6, but my test only showed 2.4 mpg more and maybe 3.5 mpg if I had not caught that last light. Also the 2.4 was not yet broke in with only 1,000 miles.

    Hope this helps the discussion some. I will be taking a trip in two weeks and will report the results and back the figures up with hand calcs. I will also use my GPS to check for speedometer error.
  • All, Thanks for your tips and encouragement. Yesterday I measured my 44 mile trip and got 24.3 MPG. I had the AC off, tire pressures at 35PSI. So there is some light at the end of the tunnel here!
    Mazda6due, I've been doing tip (1) for years. I understand (2) but find it practically hard to do it with my highway as the traffic is unreliable. (3) is new to me but I don't think I want to do it. I want to save mileages, but I don't want to try it too hard either. I want to be relaxed and enjoy my drive.
    I hope it is true that after the break-in period or after 5000 miles, the mileage will be improved. But I am skeptical about it.
    I will let you know my mpg for the next tank
  • bibo2bibo2 Posts: 9
    I got 25.1 mpg for my tank this week based on my calculation. DIC shows only 23. It seems to be steady at that mpg for my driving.
  • In July my wife, 9-year old, and I took a vacation to Bush Gardens in Williamsburg VA with plenty of luggage. The drive from Baltimore was about 200 miles each direction. We have a 2008 Malibu LTZ, 3.6 6cyl, w/ 6 speed auto transmission.

    On the way there, which included about a 1 hours back-up near Quantico, we averaged just over 29 MPG.

    On the way back - and I swear to you, I'm not exaggerating - we averaged 32.2 MPG. Must have been a downgrade or tailwind for the majority of the miles.

    My daily commute is 35 miles each direction, about 80% of it is highway, and I average between about 26.5 MPG week in, week out. With a 50/50 mix of city/hwy, I get about 21-23 MPG routinely.

    My wife does not get as good of mileage as I do - our driving styles are very different. She averages about 19-21 with a 50/50 mix of city/hwy.

    Regards,

    Misha
  • I took my first long trip recently, from Pittsburgh to Manassas Va. The car had 5300 miles on it, 37 psi in tires (warm), 55 degrees out, no A/C used. I took the mountain route, lots of up and down grades. I was in 4th and 5th gears climbing the hills and the same gears going downhill to keep off the brakes. I averaged 28.2 MPG over a 181 mile leg under those conditions. My average speed was just under 50 mph. I noticed that the transmission does not shift into 6th gear unless the car is going over 45 MPH. I made extensive use of the manual mode and the tap shifters on the hills. That way I could drop into 5th gear instead of having the auto mode drop into 4th gear from 6th. The result was that for the gentler hills, I never had to go to 4th gear. For the longer or steeper hills, I had to go down to 4th from 5th when appropriate. I was also able to go to 6th sooner than the auto mode would have upshifted me as I crested the hills. I kept forgetting that I had to upshift from the lower gears when in manual mode. A few times, I was stopped at a light in manual mode and the engine rev-ed high when the light changed and I did not upshift. I now put the transmission back into auto mode when I stop.

    Needless to say, I was very pleased with the mileage under those unfavorable conditions. On the next leg of the trip (57 miles) using freeways only and traveling 60 - 65 MPH, I averaged 33.6 MPH. I checked my speedometer using my GPS and it was 237.9 miles (car) and 237.2 (GPS). When I hand calculated my mileage, I found that the car's computer over estimated MPG by 3% or about 1 mph too high. Still happy with the results.

    On the return trip, I averaged 33.5 MPG on the expressway using the A/C this time, but saw the MPG fall off to 27.3 when I hit two lane highways, traffic and traffic lights (before 3% error reduction).

    I expect to get 34 MPG on level uncongested highways and accept that hills, traffic and lights must reduce this figure commensurate with the distance travelled under less favorable conditions.

    By comparison, my 2000 Chevy Venture van with a 3.4 - 4spd automatic, rarely hit 30 MPG on the trip computer which always read 5% high or about 1.5 MPG less true mileage. The difference was due to weight, aerodynamics and the engine/transmission efficiencies.

    When I feel that my MPG levels off, meaning that my engine is fully broken in, I will switch to synthetic oil to maybe get even better mileage. If you use synthetic too soon, you may not allow the engine to break in sufficiently.
  • malexbumalexbu Posts: 169
    An interesting report... But I am curious about these statements:

    When I feel that my MPG levels off, meaning that my engine is fully broken in,

    When (at how many miles, approximately) do you expect your engine to be fully broken in? With your current mileage just under 6K, isn't it already? (The Malibu manual mentions only 500 miles for engine break in).

    I will switch to synthetic oil to maybe get even better mileage.

    A good idea, in any case.

    If you use synthetic too soon, you may not allow the engine to break in sufficiently.

    And what happens? I use synthetic only since under 3,000 miles -- what bad things should I be looking for at my current 30,000 (or later)?

    Thanks!
  • My Aura was a demo with 5000 miles and I have only put 1000 miles on it. So I can't say what the MPG was when it was new or if there has been a significant increase in MPG. The car's rings are probably already fully seated. I just want to continue checking the mileage until 10,000 miles to see if there is an additional improvement. The only reason that one would change to synthetic oil is for better mileage (through less friction) and to reduce engine wear. So, if one would use synthetic too soon, then the friction reducing results would not allow the rings to seat through wear. There are so many opinions out there about the proper break-in procedure that one has to decide for themselves after doing their own research.

    There are plenty of posts about mileage continuing to improve up to 10,000 miles. So, I decided to evaluate mileage until then before using synthetic. I have had many cars that I never used synthetic in, so I see no reason to go to synthetic early.

    Break-in is the mating of the cylinder rings (oil and compression) to the cylinder walls, and insufficient mating results in oil consumption, blow-by, tighter clearances and lower MPG. In your case, 3000 miles should be a sufficient break-in period, but more may be better. Or, more may also be unnecessary. Since I can't say for sure, I have to make a determination. I think that by my mileage results (33+ under ideal highway conditions), the car should be already broken-in, but I am in no hurry to decide to discontinue the break-in process by going to synthetic after only driving it myself for 1000 miles.

    I based my opinions on reading and reasoning since I have never performed a controlled break-in experiment where engines were torn down after differing break-in procedures. So, please don't think that less of a break-in period is insufficient based on what I have posted. Some exotic engines come from the factory with synthetic oil, but I believe that they have a better engine building process and/or have break-in performed at the factory.

    I would like to know if anyone has kept records on MPG before and after switching to synthetic oil?
  • malexbumalexbu Posts: 169
    I just want to continue checking the mileage until 10,000 miles to
    see if there is an additional improvement.


    This is, obviously, a very reasonable intention -- and I am as
    interested as anybody in learning the results.

    So, if one would use synthetic too soon, then the friction reducing
    results would not allow the rings to seat through wear. There are so
    many opinions out there about the proper break-in procedure that one
    has to decide for themselves after doing their own research.


    See, when I switched to synthetic in my still very young Bu, I did a
    lot of reading about oils and break-in procedures and concluded that
    for modern engines, manufactured with extremely high precision, the
    old rules don't apply: there is practically no break-in period
    for them and the sooner you switch to synthetic, the better.

    There are plenty of posts about mileage continuing to improve up to
    10,000 miles.


    Don't know... I am very interested in this topic but wasn't able to
    notice the trend in reported facts -- only the "I hope it will happen"
    one.

    Can't say I saw a meaningful improvement myself -- and I watch MPG
    carefully. What does matter a lot, are road conditions, temperature
    and the driving patterns. I definitely drive gentlier now than 30,000
    miles ago.

    In your case, 3000 miles should be a sufficient break-in period,
    but more may be better.


    I suspect so -- haven't seen anything bad yet :-)

    I based my opinions on reading and reasoning since I have never
    performed a controlled break-in experiment where engines were torn
    down after differing break-in procedures.


    This is my point, exactly: few (he-he...) people have performed such
    experiments, so while the reported MPG numbers are very interesting,
    for those who care (and thank you for your meticulous report!), I am
    afraid your statements about the break-in period and processes cannot
    be reasonably substantiated -- they are a part of a mysterious
    legend. Could be true in the past -- doesn't mean it's true now. If
    there were a need for an extended break-in period (beyond the 500
    miles the manual mentions), or special oil change considerations, they
    would be mentioned in the manual, as many other helpful things
    are. Nobody but the manufacturer has the resources and incentives to
    evaluate the engines' life -- and tear some apart in the process.

    I would like to know if anyone has kept records on MPG before and
    after switching to synthetic oil?


    Why, I did -- here are appropriate MPG samples for my two Malibus:

    --------------------------------------------------
    Car 1
    -----
    26.00
    28.04
    21.72
    27.39
    27.23
    27.63
    29.23
    ----- 3138 miles: OEM -> Mobil-1 Synthetic
    26.18
    25.01
    21.34

    Car 2
    -----
    27.25
    24.54
    26.30
    28.02
    25.96
    23.30
    ----- 5414 miles: OEM -> Mobil-1 Synthetic
    25.62
    24.82
    27.89
    25.06
    24.95
    --------------------------------------------------

    Do you see a trend here? Neither do I... :-)
  • From those figures, synthetic didn't make a difference. Of course, every tank was under different driving circumstances and they were not controlled tests.

    Today, I made a 180 mile highway round trip and was eager to get over 30 MPG again. I was only averaging 28.4 MPG after 140 miles. I was on my way home and completing the leg that had a downhill bias. I got up to 30 MPG about 30 miles from home and then I hit road construction and sat for 15 minutes inching along. Needless to say, the whole exercise was useless as my mileage fell at that point and if I ended it at the road construction (30 MPG), then I lost the down hill leg of the trip.

    Since I am retired, no two tank fulls are similar. I don't travel the same roads to and from work every week. That's why I look for highway trips that can give me a maximum reading. If I can attain say 32 MPG a few times with 6000 miles on the car and still get 32 MPG at 10,000 miles, that will tell me that my MPG gains has leveled off. If I then switch to synthetic and can attain 34 MPG a few times, then that will be a meaningful improvement. If I still get 32 MPG while on synthetic, then I will conclude that synthetic may not be worth the cost. I may then look for other intangibles such as lower operating temperatures or increased engine life. But that is a topic that will need to be researched by me if MPG does not improve. It will take until the end of next summer for me to get that many miles on the car.

    A further note on today's trip. I was in the manual mode in 6th gear when I passed a car on a two lane road. I had plenty of room to pass but needed to pick up some speed as a vehicle came over a hill at me. I was not picking up speed and I punched it to get over without result. I still got over in time, but was momentarily disturbed at what would have been the outcome if I needed the "passing gear" to avoid the car. I then realized that when in the manual mode, there is no "passing gear" unless I tap the transmission down two gears. This was the first time that I was in manual mode and needed to pass someone quickly. This car is still new to me and I am still learning the nuances of this type of transmission. Needless to say, this will not happen again. I will either use the auto mode when passing or be prepared to downshift manually from now on. While I understood what happened, it was not soon enough to suit me. I mention this only because anyone who has and uses the manual mode may find themselves in the same situation some day. Perhaps this is addressed in the owners manual, I'll have to read it.
  • phil53phil53 Posts: 54
    I just switched to synthetic in my '09 4 cyl on Friday at 1900 miles. I've been quite disappointed in fuel mileage so far. I've never gotten over 26 mpg so far. I went camping this weekend and my wife drove the car around town. When I got home, the DIC showed an average of 16.3 mpg. The one thing I have found interesting is that the calculator consistantly reflects better fuel mileage than the DIC. After I've had a chance to put a few tanks in now that I have synthetic, I'll post the mileage figures for before and after.
  • While 1900 miles is beyond the recommended break-in period, I've read posts about mileage increases up to 5,000 miles or even 10,000. I also test drove a 2009 4cyl 6speed that had 1,000 miles on it and got 31.7 MPG over a 6 mile test loop. Of course, that was by the onboard MPG computer and was not checked with hand calculations. The 31.7 came from carefully driving with the intent to maximize economy. If you don't drive with fuel economy in mind, your mileage will be significantly less. What I like to do is to see what my fuel economy maximum is by driving a set course after zeroing my MPG reading and driving 10 miles on a level road at a constant 60-65 mph. If hills or wind is a factor, I drive out 5 miles and back to cancel out those factors. The only other factor to consider is if your computer has an error and how much. My 2000 Venture van reads 5% high, my 2008 Aura 3.6 reads 1% high. That you can only determine after checking several tank fulls and checking with hand calcs. You stated that your computer reads low, but not by how much. Since I have had vehicles with an onboard MPG computer for the last 15 years, I have become very sensitive to proper fuel conserving techniques. Nothing drastic like drafting trucks or coasting in neutral etc., but by anticipating slowing traffic and most importantly, not stomping on the accelerator just for the joy of it.

    The purpose of doing a MPG maximizing test is to see if your fuel economy is off or if its your driving style. To me, highway driving is 100% highway, not 80/20 or any other combination. If you still can't get 33 MPG or better under ideal highway conditions, you may have to consider that your break-in period needs to be extended or that you have a mechanical issue with your engine. If you go to the service department where you bought the car, they may tell you that you need to drive 5,000 miles or more before they will look at it. They may also say that just to blow you off for 6 months. But to look at it from their position, some people drive with a heavy foot and in hilly areas or mix in congested areas and speeds under 40 mph and think that they should get the 33 MPG that the computer says. If you drive under 40 mph (not sure what speed that the 4cyl transmission downshifts from 6th gear) you are not driving in 6th gear and you mileage will be less.
    So, it will take some time for you to determine if you have a problem and if it is the car or the conditions under which it is being driven.

    One other thing to check is whether your odometer is reading correctly. I checked mine on a recent trip using my Garmin GPS which tracks miles driven and had 237.9 miles (car) vs 237.2 miles (GPS). You can also drive a highway that has mile markers and compare over 100 miles. Yours should be fine but you have to check all variables to know for sure. That is another reason that service departments may be reluctant to address MPG; the fact that they don't have the time to sort through all the variables that the owner could do.

    If it were me, and all the above checks out and if the car can't get the desired MPG, then I would go back to regular oil and extend the break-in period and see what happens. Good luck, keep us informed on your results.

    Oh, and one last thought: I was riding with a friend in his car with a trip computer and he told me that his mileage was the same whether he drove in the city or on the highway. I observed that the MPG did not change even a tenth over 20 miles. I asked him if he reset the computer after each fillup and he didn't know what I was talking about. Turns out that he had nearly 100,000 miles of driving in his data base, and as soon as I hit reset, the tripcomputer began showing results. So, I mention this only because you never know who reads these posts and their understanding of the variables.
  • phil53phil53 Posts: 54
    I won't kid anyone. While I have been driving with one eye on the DIC, I don't drive in a manner to maximize fuel mileage - just an effort to improve my results over the manner I might ordinarily drive. My commute is about 75% freeway and 25% suburban streets. Traffic is not as bad as in some larger cities. Portions of my commute are run at 75 mph. I generally drive about 5 over.
    So I don't expect to get 33 mpg in routine driving. But, on my other GM products (an Avalanche and a Corvette), I pretty regularly get the EPA ratings - and that under the old rating system. On this car, I'm not even matching the new ratings.
    I probably won't make a big deal out of it with the dealer. I do want to wait until I can take it on a road trip to see what my actual highway mileage is. I will mention it to them, though. I have a pretty good relationship with the dealer - owner, service manager, service writer, etc. They've always treated me well.
    I'll let you know how it goes. And I'll post the mileage - both DIC and calculator.
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