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Americans Have No Idea How Much Fuel Idling Uses - YouTube
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hello everyone and welcome how much fuel
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do you think it takes to start up an
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engine another way of asking this
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question how much time does it take an
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idling engine to use the same amount of
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fuel required to start up an engine now
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if you knew the answer to this question
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you could potentially save fuel if you
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knew how long you were going to be
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sitting in a stoplight or something like
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that perhaps a train is crossing by and
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you could also answer whether or not
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start stop systems in modern cars are
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actually doing anything now according to
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a study published in the journal of
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energy policy they asked 1300 u.s
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drivers how long they thought it would
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take before it was more beneficial to
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shut an engine off rather than let it
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idle and the average response amongst
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1300 participants in that study was 3.6
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minutes the good news is we don't have
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to guess or ask our uncle or cousin or
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whoever about how much fuel an engine
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uses while it's idling it's well
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researched the data is out there you
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just have to go and read it and so this
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is how much fuel a small four-cylinder
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engine will consume while idling for 3.6
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minutes and this is how much fuel it
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actually takes to start that same engine
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up small four-cylinder engine so this is
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what the average american thinks it
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takes to start up a four-cylinder engine
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and this is how much fuel it actually
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takes to start up a small four-cylinder
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engine now if you're embarrassed because
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you're an american and you had no clue
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how much it takes to start up an engine
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don't worry i'm sure plenty of the rest
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of the world also didn't know how much
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fuel it takes to start up an engine i
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mean i didn't know
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wait i'm american
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so no more guessing in 2004 a study
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published in the journal of sae sought
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to find out whether or not engine start
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stop systems actually improve fuel
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economy the study took two identical
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cars both with 1.5 liter four-cylinder
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toyota gasoline engines and they
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equipped them with fuel flow meters so
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they could measure the fuel going into
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the engine being consumed now to get a
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baseline measurement of the engine's
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idling fuel consumption they idled both
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vehicles in both park and then in drive
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for 90 minutes and measured how much
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fuel they used during those 90 minutes
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you then do a little bit of division and
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you come down to the fuel flow rates for
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an idling engine so this is how much
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fuel an idling 1.5 liter engine uses in
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just 10 minutes so if you had six of
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these that would tell you how much it
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uses in an hour so it's about .63 liters
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or about one sixth of a gallon that this
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idling engine will use every hour and of
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course if the displacement of that
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engine is larger then it's going to use
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even more than this it's also
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interesting to note that there really
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wasn't much of a difference between
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having the car in park and having the
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car in drive as far as how much fuel it
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was consuming while idling so next they
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wanted to find out how much fuel does it
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take to start up an engine and so in
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order to do this they started and
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stopped the engine a ton of times
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basically what they did is they did they
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started they stopped it they started
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they stopped it until it had used the
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same amount of fuel that the engine had
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used while spending 90 minutes idling
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from there it's a pretty simple equation
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you take the total amount of fuel used
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and you divide it by the number of times
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that you started the car and that's
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where they came up with the 1.1 to about
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1.2 milliliters of fuel required in
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order to start a 1.5 liter engine okay
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you're still following right so if you
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take the amount of fuel required to
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start up the engine and you divide it by
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how much fuel the engine uses while
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idling in fuel per second then you get
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how many seconds does this engine have
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to idle in order for it to be more
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beneficial to instead simply shut it off
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so if you take 1.2 and you divide it by
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0.171
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cc per second which is the fuel rate at
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idle then you get about seven seconds so
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if this engine is idling or a 1.5 liter
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four-cylinder engine is idling for seven
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seconds if it's going to idle for any
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longer it's more beneficial to simply
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shut it off and then restart it once
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traffic is moving again now i'm sure
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this is where plenty of your heads start
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exploding you say jason it's not safe to
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turn your car off in traffic or i need
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my ac look i'm not telling you how to
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live your life or drive i don't really
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care what you do what i'm telling you is
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just the data behind fuel consumption so
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if you want to save fuel if that was
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your only goal how you drive is your
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business do whatever you want to do but
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just letting you know after you let that
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engine idle for longer than about seven
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seconds your wasting fuel had you just
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let it shut off so that's the
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justification for a lot of the systems
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out there which do have start stop which
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by the way they have completely
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different starters which are used to
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start those up so they're built for many
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more repetitions many more starts and
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stops they're designed for it from the
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start it turns out engineers are capable
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of thinking about these things knowing
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that hey if you use a starter a ton of
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times you probably need to design for it
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they do it don't worry about it so if
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you do want to save fuel using a start
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stop system what this is showing is that
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if your car is shut off for longer than
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seven seconds then it could be
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beneficial wait come back i see that
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mine wandering on me again now you're
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thinking jason but this isn't a 1.5
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liter engine so surely in a larger
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engine you know maybe that doesn't it
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maybe it's longer than seven seconds
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well you know that could be but here's
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the thing the larger engine is not only
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going to require more fuel to start up
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it's also going to require more fuel to
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idle so the ratio may remain somewhat
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similar so estimating about seven
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seconds eight seconds nine seconds isn't
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that crazy to do because as the engine
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gets larger it takes more fuel to start
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up it takes more fuel for it to idle
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okay now we get to the final part of the
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study and this is really cool so what
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they wanted to find out was whether or
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not engine start stop systems actually
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save any fuel and so what they did is
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they took both vehicles they equipped
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one of them with a start stop system and
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then they had the other always running
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when it came to a stop so the engine
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would idle at a stop versus the other
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one would shut off whenever it came to a
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stop so they took both of these vehicles
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and they drove the same route in four
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different ways so four different types
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of traffic so it was you know real world
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driving uh just using real traffic and
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they just put one car right behind the
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other and this is city driving so we
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don't have to worry about aerodynamics
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playing a role here the front car you
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know towing the car behind it uh the the
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speeds are very low so real world city
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driving test to show you know does this
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actually save you any fuel uh you know
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when of course start stop systems are
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designed to save you fuel in-city
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driving and so the cars are right behind
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each other they're driving the exact
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same route and the exact same traffic
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and they range from light traffic to
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heavy traffic and what they found is
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that in all four of those scenarios the
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car with start stop actually got the
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best fuel economy and so it ranged from
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about four percent better to as high as
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8.7 better fuel economy with the car
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that did have start stop equipped okay
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so what have we learned well first of
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all it takes very little fuel in order
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to actually start up your car just about
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1.2 milliliters to start up a 1.5 liter
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four-cylinder engine especially when
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comparing that to how much fuel an
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engine uses while idling we also learned
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that if your engine is idling for longer
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than about seven seconds you're actually
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starting to waste fuel and finally real
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world city driving shows that you can
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actually save about four to eight point
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seven percent in fuel economy by using a
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start stop system versus just letting
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the engine idle when you come to a stop
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now of course feel free to let me know
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in the comments below why everything
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about this video is nonsense thank you
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all so much for watching
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