MPG ratings

Discussion in 'General Motoring' started by NJ Vike, Sep 7, 2005.

  1. NJ Vike

    NJ Vike Guest

    Just saw on the news this morning that most MPG estimates for Highway but
    for city driving, they were drastically off.

    Does anyone here feel they are getting the gas mileage that the sticker

    "Now Phoebe Snow direct can go
    from thirty-third to Buffalo.
    From Broadway bright the tubes run right
    Into the Road of Anthracite"
    Erie - Lackawanna
    NJ Vike, Sep 7, 2005
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  2. NJ Vike

    maxpower Guest

    You wont and never will. they do it on a dynameter with no load, no cold
    start ups either
    maxpower, Sep 8, 2005
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  3. NJ Vike

    Matt Whiting Guest

    I've always achieved very close (within 10% and often closer) to the
    highway mileage with all of vehicles I'ved owned in the last 20 years.
    Then again, I drive mostly on rural highways, stay pretty close to 55
    MPH and don't accelerate and brake like a maniac.

    Matt Whiting, Sep 8, 2005
  4. I've been monitoring my Crossfires milage. It was rated 17 city, 27 highway.
    Overall, in the first 15,000 miles, I've averaged 25.3 which is reasonably
    close for combined city/highway.
    Richard H. Brockmeier, Sep 8, 2005
  5. NJ Vike

    Steve Guest

    The last 3 new cars in my family (1992 Dakota 5.2L, 1993 Vision TSi
    3.5L, and 2000 Durango 5.9L) have all gotten a few MPG BETTER than the
    EPA highway rating, and were almost spot-on for the "combined" rating.
    The Dakota, in particular, just blew the doors off the EPA highway
    rating. Nearly 5 MPG better. Of course, as they say, "your mileage may
    vary." :)
    Steve, Sep 8, 2005
  6. NJ Vike

    Matt Whiting Guest

    What combined rating? I don't recall seeing this on any window
    stickers. Is this a new EPA rating?

    Matt Whiting, Sep 8, 2005
  7. We have a 2005 T&C with 3.8 engine. It is rated at 18 city 25 highway. We
    have about 5000 miles on it. On a long highway only trip where we averaged
    about 70mph, we managed just over 24mpg. Not bad. We have never been able
    to get near the 18mpg city rating. We usually get about 15 or so. In combined
    driving we get about 17mpg.
    Alex Rodriguez, Sep 19, 2005
  8. NJ Vike

    Bob Shuman Guest

    We have a 1999/70K miles with the same engine and my wife gets between 13
    and 14 around town. We can get 26 or so on the open road at 55MPH, but
    higher speeds decrease mileage.

    Bob Shuman, Sep 19, 2005
  9. The 300C does better then Consumer Reports says but worse than the
    sticker. EPA of the car is 17 city, 24 highway. I'm averaging between 16
    and 17 so that's pretty close but that includes highway driving. On short
    trips, 7-8 miles, it gets 13 which is awful but better then the 10 that
    Consumer Reports says it gets. On long highway trips (100 miles) I get
    around 19. On a single occasion I managed to peak at 23 on a highway trip.
    General Schvantzkoph, Sep 20, 2005
  10. NJ Vike

    C-BODY Guest

    For ALL of you out there with a factory installed trip computer that
    will read "Instant Fuel Economy", I strongly suggest you put it in that
    mode and learn to drive by it. It is HIGHLY revealing as to fuel
    economy and how it is affected by driving style and sitting in traffic.

    It used to be that the bulk of Chrysler's factory trip computers
    (especially on the LH cars) would read "Inst Eco", but in the later
    years it seems that this function has been deleted on some vehicles. Of
    course, all of them have "Ave Eco" readings, which can help as when you
    punch "Reset" at particular times, it'll first give the "instant"
    reading and then settle back in to its "average" cummulative readings.

    On the Charger R/T I rented (an upgrade from a Taurus) recently, I found
    it interesting that you had to get the upgrade steering wheel controls
    to get the trip computer.

    Now, back to the city driving fuel economy ratings and driving style.
    If you have the "Inst Eco" feature, you'll notice single digit numbers
    when pulling away from a stop sign, usually until you get into 2nd gear
    and then it'll go to about 12mpg until you get to crusing speed, back
    out of the throttle, and stabilize the speed. Being stopped at a stop
    sign or red light or fast food drive-thru all impact the fuel economy
    much more than you'd suspect too.

    The difference in a 6mpg acceleration (reasonably brisk) and an 8mpg
    acceleration (slow) is not that different, but the 6mpg acceleration
    will get you to your desired speed . . . AND the more economical
    cruising speed . . . quicker such that overall fuel economy is
    increased. Hence, less time spent in lower fuel economy areas and more
    time spent in higher fuel economy areas.

    Modern cars and trucks will coast much farther than you'd suspect too.
    Remember the old fuel economy tip of anticipating stops? Well, when a
    fuel injected vehicle coasts, it also goes deeper and deeper into "fuel
    shut-off" mode. So, use the quicker acceleration to get to the desired
    town speed, try to get in the traffic pattern that will let you hit all
    of the lights on green, and if you see slower traffic ahead, take your
    foot off the accel pedal and let it coast rather than driving right up
    to it and then using the brakes. The longer you coast, the more fuel is
    taken out of the system, up to an indicated reading of 99mpg on the
    computer display.

    Also, using the factory cruise control is a boon to trip economy.
    Especially on the more finely controlled current era vehicles.

    Once the cruising speed is reached, the computer will keep the vehicle
    speed highly constant. It'll throttle into the engine going up hills
    (sometimes as low as 15mpg), then trim the throttle back IMMEDIATELY as
    the hill is crested, and then also back out of the throttle going down
    the other side (going into "coast" and the resultant "fuel shut-down"
    modes). If you try to "foot drive" it, we all will try to maintain the
    speed up the hill, but forget to back out once we get to the crest and
    then head downward. The higher speeds reached at the crest and on the
    downslope, before we realize we're going too fast and then back out of
    the throttle, are not as economical by a significant amount as letting
    the cruise do the work. This is highly apparent when you try it both
    ways and watch the "Inst Eco" readings!

    At cruising speed, the difference in 30mpg and 22mpg at the same speed
    is a very minute difference in pressure on the accel pedal. Not like it
    used to be with carburetors! On the modern fuel injected vehicles, as
    soon as you put more pressure on the accel pedal, it's feeding
    additional fuel "right then" rather than letting additional air flow
    through the carb venturi pull the added fuel into the intake air.

    I never did get what I'd call a decent mileage check on the Charger R/T
    HEMI, but it's probably right at posted EPA Highway on the highway.
    Using the cruise at approx 65mph road speeds.

    There's a posting in the LXForums website on how to rig a light to tell
    when the Hemi's MDS system is operating.

    Bad thing is that a <$24K 2006 Impala LT has a standard trip computer
    (with Inst and Average fuel economy displays) and you have to pay extra
    to get it on the Charger. Oh well . . .

    From experience, the EPA highway ratings are a little conservative
    compared to what the vehicles can actually produce. The "City" ratings
    can be more variable due to individual diving styles and locales
    compared to the IM240 driving cycle (where the readings for the EPA
    sticker are based).

    When the LH cars were new, the best I'd get from an LHS on a highway run
    (by the computer readout) was an average of 26mpg. The 2nd gen 3.5L V-6
    300M would get 31mpg at 55-60mph, dropping to 27mpg at 90mph (about
    700rpm difference in engine speed).

    By observation, one thing that really hurts actual fuel economy is
    aerodynamics. For comparison, look at the body sillouhette of the first
    gen LH car Concorde and the LHS. Whereas the LHSs would get an average
    26mpg on the highway runs I did, the Concordes would to 27.5mpg. A
    slicker "over the top" contour plus a less blocky front end contour.

    Now that my parents' '95 LH car New Yorker has reached the 80K mile
    level, it gets better cruise economy than at lower mileages, generally
    hitting the 30mpg mark as the 2nd gen 3.5L V-6 will, and with generally
    a 23mpg average in the way my mother drives (mixed rural highway and

    Now, while everybody loves the strong and bold styling of the new
    Chrysler 300s and Dodge Charger, that blocky frontal shape and roof
    design is costing real world fuel economy compared to the prior
    generations of LH cars. Figure into the mix the new HEMI and how nice
    it runs and it's a set-up for somewhat disappointing fuel
    economy--especially in "town" driving, MDS or not.

    Hopefully, this might explain some of the reasons behind what real world
    fuel economy can be versus what Consumer's Reports might report.

    If you have any concerns about your particular vehicle, I suggest you
    take it on a highway/Interstate loop run during non-peak traffic times.
    Find a gas station that has an easy off-ramp nearby and hopefully an
    easy on-ramp to the highway. Then plan about a 60 mile loop around your
    metro area, which should take about an hour to complete, using the same
    gas station as the end point.

    Top off the tank, letting the pump click off and then manually getting
    it that last .3 gallon by doing it yourself. Then accel briskly to
    crusing speed and set the cruise control on the highway. Using cruise
    "+" or "-" buttons to vary the speed, while watching well ahead for
    changing traffic speeds and conditions and punching the buttons to vary
    the speed accordingly.

    Then, at the end of your loop, punch the cruise off and coast to the end
    of the off-ramp and drive to the (hopefully) same gas pump and parked
    heading the same direction as when you filled the tank. Once again,
    fill the tank and count the fuel used as when the pump first clicks off.
    If it's accurate, the second cut-off with the manual fill will be the
    same as the first time. On the second fill amount, do it slowly rather
    than "full blast" so it'll be more accurate.

    Now that you have our highway mileage and your fuel used (at the first
    click off), you can figure your fuel economy for that type of operation.
    Hopefully, it'll be at or above the EPA highway ratings. In some cases,
    you might be surprised at how high it might be, compared to what you
    "thought" it was doing.

    I hope this has helped explain some of the fuel economy issues regarding
    modern fuel injected vehicles and how to exploit them to better fuel

    C-BODY, Sep 25, 2005
  11. NJ Vike

    Bill Putney Guest

    Quite an extensive and thought-out write up.

    I am surprised, with all the detail you did go into, that you did not
    mention affects of the cruise control downshifting to maintain the
    setpoint window on rolling hills terrain - particularly since you
    mentioned owning LH cars which definitely do this (to a point of
    annoyance at times, though it is better than getting tickets). Of
    course it is bleeding off energy that has to be made up when the terrain
    levels out and slopes upward again, and that costs gas mileage just like
    braking to accomplish the same thing would.

    But if you weren't in cruise control, you would be having to either
    manually downshift or use the brakes to keep within the same
    ticket-avoidance window that the cruise control is attempting. I find
    that to really be safe from tickets, I have to take manual control in
    some way - usually I use your anticipation technique and move the
    setpoint down 2 to 4 clicks (depending on the amount of slope - 1 mph
    per click) before starting on the downslope, and I still get the
    inevitable energy-robbing downshift, but I force it into play earlier by
    dropping the setpoint (and bumping it back up at the bottom of the hill)
    - otherwise I find myself at risk of a speeding ticket. Maintaining the
    same setpoint and letting it drift upward in speed 5 to 7 mph to gain
    fuel economy over the risk of getting a ticket would make as much sense
    as running red lights for better fuel economy. So it's another
    economy-killing reality that we gladly put up with to reduce/eliminate
    insurance rates and fines.

    I also find the 'up' (2 mph per click) and 'down' (1 mph per click)
    speed settings adjustment to be *very* convenient for some of the
    reasons you said and what I added above. If I want to bump up 1 mph,
    without even thinking, I click up once, and down once. In extreme cases
    (steeper slopes), I manually downshift ahead of time (pretty much the
    same effect as lowering the setpoint). And, I find myself with my foot
    off of the gas pedal and using the cruise buttons to fine tune my speed
    during most of my mostly-55-to-60-mph-40-mile-each-way daily commute
    (using the gas pedal only for the occasional stop light and one small
    town that I pass thru).

    Bill Putney
    (To reply by e-mail, replace the last letter of the alphabet in my
    address with the letter 'x')
    Bill Putney, Sep 25, 2005
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