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Serious drop in MPG

Discussion in '2nd Gen. Tacomas (2005-2015)' started by rpoint16, Dec 12, 2009.

  1. Dec 12, 2009 at 9:41 AM
    #1
    rpoint16

    rpoint16 [OP] Well-Known Member

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    I have aprox 25K miles on my 08 V-6. After installing my lift last year, I have religiously been getting 19.2 to 19.1 mpg city/hwy for a year. All of a sudden 4-5 months ago (aprox 7-8 tanks of gas) my mileage dropped to 17 MPG. Same gas station, same driving habits, etc…

    I took it to the dealership under warranty. They did a diagnostic & checked for exhaust leaks & all was fine.

    I know AZ has winter gas at times, but this has never affected mpg.

    Any ideas???
     
  2. Dec 12, 2009 at 9:43 AM
    #2
    08pretaco

    08pretaco Almost there

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    your due for a 30k soon, maybe changing all that shitty oil outta everything will allow the trucks gears to flow better and have everything run smoother
     
  3. Dec 12, 2009 at 9:47 AM
    #3
    T0LLPHR33

    T0LLPHR33 Well-Known Member

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    don't the winter blends of gas make it less efficient...or something like that...at least that's what i've been told and that's my understanding...:confused:
     
  4. Dec 12, 2009 at 9:48 AM
    #4
    rpoint16

    rpoint16 [OP] Well-Known Member

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    I was thinking that as well. I am current & fanatical on all maintenance, oil, filters, etc... A consistant 12% decrease in MPG is pretty significant.
     
  5. Dec 12, 2009 at 9:49 AM
    #5
    javajunk-e

    javajunk-e Well-Known Member

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    I just mentioned this to my dad, cause my last tank of gas did not take me very far. He said that it could be the winter gas, he has not been getting very good gas mileage in his Honda Odyssey or his CRV. :confused: I am due for a oil change in 1000 miles but this has never happened before... I will be watchin' this post!
     
  6. Dec 12, 2009 at 9:49 AM
    #6
    08pretaco

    08pretaco Almost there

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    ya they do but he said its never affected him before. so then i jumped to something else.

    but ya winter blends have more ethanol reducing the volume of gas and ethanol burns damn quick. take a look at the flex fuels from chevy...they say flex fuel but when they fill up the truck with ethanol blend they get what something ridiculous like 130 miles to a tank. dont quote me on that but i think thats what i read somewhere
     
  7. Dec 12, 2009 at 9:51 AM
    #7
    4low2go

    4low2go Well-Known Member

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    Do they add methanol to your gas? I have found much better mileage from gas with no methanol. I think there is less in the higher octane versions, can anyone confirm this?
     
  8. Dec 12, 2009 at 9:53 AM
    #8
    08pretaco

    08pretaco Almost there

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    i think its ethanol they add
     
  9. Dec 12, 2009 at 9:55 AM
    #9
    08pretaco

    08pretaco Almost there

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    found this

    yes. winter gas would freeze if not for anti-freeze (not ethylene gycol) components that are added. they do take up space, but dont burn. this reduces the amount of energy in a gallon of gas by 3-8% depending on location

    according to a "Modern Marvels" show the #1 cause of reduced gas mileage in winter is the increased density of cold air which can reduce efficiency by as much as 15% in some areas (probably Minnesota, North Dakota and Alaska)
     
  10. Dec 12, 2009 at 9:57 AM
    #10
    TX TRD Runner

    TX TRD Runner Well-Known Member

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    It is ethanol.
     
  11. Dec 12, 2009 at 10:00 AM
    #11
    08pretaco

    08pretaco Almost there

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    Q I am wondering why my '98 Ford Ranger gets noticeably poorer gas mileage when the weather gets colder. The vehicle has 110,000 miles on a 4.0L engine. It is four-wheel-drive. During the summer months I can get 16 to 18 mpg. In the winter it drops to 14 to 15 mpg. I keep the tires properly inflated and let the car idle very infrequently, other than to warm it up for a few minutes. Does the cold air somehow affect gas mileage? Does operating the heater affect gas mileage, much like the AC does in the summer? I notice a drop in mileage even when I don't use the 4WD.

    A Three words: "time to temperature." In cold weather, our vehicles take a much longer period of time to reach full operating temperature. And they take this extra time each and every time we start them up, even if they have not fully cooled down.

    Modern engine-management systems are very efficient at optimizing the fuel/air ratio entering the engine. The oxygen sensor monitors the percentage of oxygen in the exhaust, compares this with the percentage of oxygen in the atmosphere, and generates a low-voltage signal that communicates this ratio to the computer. The computer then adjusts the pulse-width of the fuel injectors -- the precise period of time each injector is open on each injection cycle --to fine-tune the amount of fuel reaching each cylinder.

    The system makes this very fine adjustment dozens of times each second, working very hard to reach the optimum air/fuel ratio for any given situation, and at steady-state cruise speed seeks to approach the perfect ratio of 14.7 to 1, called the stoichometric ratio. The system is running in a "closed loop" when it is relying upon the oxygen-sensor signal to fine-tune engine operation.

    But the engine-management system can seek this optimum air/fuel ratio only when the engine is up to full temperature. In fact, the computer does not look for a signal from the oxygen sensor until it approaches full temperature. During the warm-up cycle -- which takes considerably longer in cold weather -- the computer operates on a warm-up program based on coolant temperature, mass airflow or MAP sensor input of air volume and temperature, throttle position and engine rpm. This is called "open loop" operation, meaning the system is not operating off the feedback from the oxygen sensor.

    In open-loop operation during the warm-up period, the engine requires -- and is provided with -- a richer air/fuel ratio to ensure good combustion.

    It needs this extra fuel for the simple reason that a percentage of the atomized, then vaporized, fuel delivered to the engine condenses into liquid gasoline on cold internal engine components such as the intake manifold, intake valves, pistons and cylinder. And remember, it's gasoline vapor, not liquid, that burns.

    Until those parts warm up, the engine needs more fuel to operate with reasonable drivability. Thus, the colder the weather, the longer it takes for your engine to reach full operating temperature and closed-loop operation, and thus the more fuel the engine uses to deliver the same driving cycle. That's the primary reason your engine consumes more fuel in winter driving.

    Another factor in winter mileage is air density, defined as the number of air molecules per cubic foot of air entering the engine. Remember that 14.7-1 air/fuel ratio? That means 14.7 parts of air are mixed with one part of fuel for the perfect air/fuel ratio -- that's a lot of air!

    In winter, colder air means denser air -- more molecules per cubic foot. At any specific throttle setting or opening, the same number of cubic feet of air, but containing more air molecules, will enter the engine. The computer will provide more fuel to create the proper air/fuel ratio at that moment. This is a bit more subtle, since "more air/more fuel" produces more power, so you may be able to operate at a slightly lower throttle setting -- sort of rebalancing the equation.

    The bottom line with your Ranger is that you are experiencing a normal reduction of fuel mileage -- about 10 percent -- in winter driving. Be thankful it's not more than that!
     
  12. Dec 12, 2009 at 10:02 AM
    #12
    aaronk

    aaronk Well-Known Member

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    4-5 months ago it started, I don't think they come out with the winter blend of gas in July in AZ do they?

    I'm thinking since you're approaching 30K it's time to change your spark plugs and see if that makes a difference. 30K is the maintenance interval on those anyways.
     
  13. Dec 12, 2009 at 10:15 AM
    #13
    HankB

    HankB Well-Known Member

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    Where did you find that?

    I found this http://answers.yahoo.com/question/index?qid=20071215195624AAChWoQ which seems to indicate that components don't even start to freeze until -97° F. (And some answers were that it doesn't freeze.)

    Water in the gas can freeze. In the good old days before ethanol in gas, we had to add gas line deicer (alcohol) to the gas which would keep the water from freezing. Unless you get a bad tank of gas or otherwise have a lot of moisture in your gas, the ethanol in the gas is usually enough to keep any moisture from freezing.

    The alcohol does burn, but produces less energy than gasoline so it does reduce fuel mileage and power.
     
  14. Dec 12, 2009 at 10:28 AM
    #14
    rpoint16

    rpoint16 [OP] Well-Known Member

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    None of my current or past vehicles have never had a noticible decrease in mpg due to the winter gas. My neighbors & co-workers who have Taco's & 4-runners have not experienced decreases.

    This is definatley vehicle specific.

    If the plugs were on the out, wouldn't it show up on the diagnostic?
     
  15. Dec 12, 2009 at 10:33 AM
    #15
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

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    The condition of the plugs wont show up on a Diag. Odds are, the NGK's in your truck are close to, if not completely, out of spec. All I have seen have been. Also, All my trucks have shown a drop in MPG this time of year (starting a few months ago) as the stations switch over to the winter blends. I have seen drops up to 20%. Also, keep in mind that if you have a short drive to work, your truck is going to be running rich longer to warm itself up. It could be the majority of the trip is spent in an open loop condition.
     
  16. Dec 12, 2009 at 11:10 AM
    #16
    snorola

    snorola Well-Known Member

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    my mileage has dropped from 20MPG to 15.5MPG in the last two months, I am putting this down to the winter gas blend, -20F days where the truck is idling a lot more to warm up and using 4x4 almost daily now on back roads.

    It sucks but what do you do... would rather pay a bit more for gas and use 4x4 instead of going in the ditch :p
     
  17. Dec 12, 2009 at 11:17 AM
    #17
    badguybuster

    badguybuster Well-Known Member

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    I am glad I saw this post. I was about to go back up to the stealership and ream some ass. I was getting 22mpg until I took it in for service. Now I am getting about 16mpg. I thought they f'd it up but we just had a cold snap. So maybe thats the culprit.
     
  18. Dec 12, 2009 at 9:52 PM
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    TX TRD Runner

    TX TRD Runner Well-Known Member

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    I am not making an argument...to the contrary this article has peaked my interest to be on the look out on this tank.

    Here is my only question though. I had always been under the understanding that heat was an engine's number one enemy. I thought the cold air would actually improve fuel economy because the vehicle is running much cooler. We are in the forties in Anna, TX tonight. I know that is not 20 below, but I thought that would be an optimum temp.
     
  19. Dec 13, 2009 at 4:37 PM
    #19
    rpoint16

    rpoint16 [OP] Well-Known Member

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    Changed my plugs today. I'll give an update after the first of the year.

    BTW, my decrease started before the winter gas switch.
     
  20. Dec 13, 2009 at 4:42 PM
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    SportyTuRD

    SportyTuRD Well-Known Member

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    at the 30K they usually do a fuel system flush...I am sure cleaning it out will help it a bit...try some over the counter fuel injector cleaner?
     
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