1. Attachments are working again! Check out this thread for more details and to report any other bugs.

mpg, mpge, epa, cafe, switching and pollution

Discussion in 'Environmental Discussion' started by austingreen, Dec 11, 2012.

  1. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    There seems to be a lot of confusion and discussion on mpg, mpge, and cafe rules. I thought I would start this thread so we can discuss it in one place instead of moving it all through plug-in discussions and testing discussions.

    mpg and mpge are about efficiency with fuel under a specific test from the refueling point. The first big point that the EPA makes is YMMV and it will vary more in a plug-in then a hybrid, and a hybrid than a pure ice car.
    The Truth About EPA City / Highway MPG Estimates - - Car and Driver

    MPGE allows a user to understand how much power they are using. The EPA does not go into your home and figure out where you are buying your power from. It doesn't check on time of charge or any of that. It does not have a chrystal ball to see how much more efficient power generation will get to fossil fuel. It just is a measure on a different test.

    Cafe is about reducing oil usage, it is not about pollution or efficiency. That is why a cng car, an e85 car, and an ev all get the same cafe boost.

    When it comes to efficiency and pollution on a phev, you need to know driving pattern and power source. After that it, you can calculate it:)
     
  2. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    There was a question on another thread - What if your electricity comes from oil?

    Like anything else we can try to find a place, and they are no many but hawaii has a large percentage from oil.

    In august Hawaii consumed 868 thousand MWh using 963 thousand barrels of oil and 67 short tons of coal.

    that makes 963,000/868,000,000 = 0.0011 barrels oil/kwh = 0.0466 gallons/kwh +
    67 short tons/868,000,000 = 0.00015 lbs coal/kwh we will discuss that later.

    Now the tesla S 60kw gets 95 mpge what is it in hawaii

    (95 mpge / 33.7 kwh/mile) / (0.0466 gallons oil/kwh) = 60 miles / (gallon oil)
    but wait, this is not oil straight out of the ground, it gets refined and shipped, and electricity gets sent out and talk about 90% efficiency. Diesel is also 1.14 x gge gasoline. Similarly lets use a coal equivelent - lets say 1lb of coal has about the energy in 0.1 gallon of oil.

    oil is (0.0466 + 0.00015 x 0.1) gallons /kwh *1.14= 0.053 gallons gasoline eqivelent oil&coal/kwh
    Let's throw it in
    95 /33.7/0.053 x 90% = 48 mpge (raw oil + coal gge)

    Let's compare that to the bmw activehybrid 5

    26 mpg x (84% refining oil) = 22 mpge (raw oil gge)
    That leaves the Tesla just a little over twice as efficient as the slower bmw on mostly the same crude. Please note even in hawaii, those numbers are juiced with renewable electricity. The tesla will even use less crude oil there than the much slower prius, but really they are in the same ball park and gas is less expensive than electricity there.

    Please also note there may be math errors or eia may have incomplete numbers for hawaii. Please correct these if you see them.
     
  3. wjtracy

    wjtracy Senior Member

    Joined:
    Sep 19, 2006
    11,309
    3,586
    1
    Location:
    Northern VA (NoVA)
    Vehicle:
    Other Hybrid
    Model:
    N/A
    ...CAFE probably needs to be changed to CAGE "Corp Average Gasoline Efficiency"
    ...MPGe probably needs to changed to GRI " Gasoline Reduction Index"
     
  4. drysider

    drysider Active Member

    Joined:
    Apr 14, 2008
    823
    332
    1
    Location:
    Liberty Lake WA
    Vehicle:
    2012 Prius
    Model:
    Four
    A better description might be that MPGe is battery to the wheel and CAFE is well to the wheel...and they are energy, not power, numbers.
     
  5. drinnovation

    drinnovation EREV for EVER!

    Joined:
    Dec 10, 2011
    2,027
    586
    65
    Location:
    CO
    Vehicle:
    Other Hybrid
    Model:
    N/A

    MPGE is wall/pump to wheel (efficiency given what we pay for) while CAFE is as much politics (with weird incentives) about reducing oil.. the use of flex fuel for truck is because of how those incentives work.
     
    austingreen likes this.
  6. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    +1
    That is exactly how MPGe is suposed to work, since mpg does not care how the gasoline got to the pump. I think you were onto something recalculating well to pump to include discovery energy. As North American's shift to more north american oil, the additional imputs to get oil sands and shale wells producing will make the process less efficient.

    For Cafe, the rules are rather simple. mpge is divided by 0.15 for alternative fuel vehicles. For flex fuel E85 vehicles it is assumed half of the miles are E85 and half gasoline. This boost for E85 flex fuel is phased out in 2016.
    Will flex-fuel vehicles survive when CAFE credits dissappear in 2016?

    An open fuel standard would allow development of methanol blends to fuel the fleet.
     
  7. drinnovation

    drinnovation EREV for EVER!

    Joined:
    Dec 10, 2011
    2,027
    586
    65
    Location:
    CO
    Vehicle:
    Other Hybrid
    Model:
    N/A
    Yeah but the flex fuel is mostly a game, not reality. in 2011 there were
    38Million gallos of E85 were produced, and with 8Million Flex fuel vehichles, that is an average of about 5 gallons of E85 per vehicle, compared to the averag o about 550 gallons, so its about 1% usage.

    So the Cafe boost assuming 50% E85 and then dividing by .15 is effectively increasing the "CAFE" mpg of those vehicles by 3x when in reality the use of alternative fuels is minimal.
     
  8. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    There is no doubt that flex fuel meant that large vehicles were allowed to have lower real mpg under cafe rules, but that loophole is closing IIRC in 2016, which means we don't need to worry about trying to repeal it.
    6 Ways Detroit Gamed the CAFE Standards - The Flex-Fuel Loophole - Popular Mechanics
    The import loophole is also closed. Unfortunately lobbiest have kept the truck loophole - if you call something a truck you get allowances even if it really is just a tall station waggon. Foot print also allows the bigger the higher consumption. Make no mistake, flex fuel rules were a little stupid, but it did allow the experiment to happen. The big problem was this SUV loophole that allows you to call it a truck, and not raising cafe levels. Cafe levels finally started rising again in the late 2000s.

    Perhaps we need open fuel standards legislation to get flex fuel to include methanol blends (m85) and continue to give the credits. They may actually help:) reduce gasoline use and substitute methanol.