What Uses Less Gas – Coasting Or Engine Braking?

Is It More Efficient To Coast In Neutral Or In Gear?
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What uses less gas? Coasting in neutral, or engine braking? Of course, the answer is it depends. A simple example? If you're approaching a red light, and know that it's going to remain red, engine braking will slow you down without using any fuel, and will be the most efficient option. If you know for a fact that the light is going to turn green before you reach it (which, you don't, but hypothetically), then it's more efficient to coast in neutral and maintain your speed, then get back on the accelerator once the light has turned green.
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Hello everyone and welcome in this video . we're gonna be answering the question is . it more efficient to coast in neutral or . engine break when going downhill and . really this will apply to either . automatic or manual transmissions in . this particular case i am in a manual . transmission 2016 subaru crosstrek and . we're really going to be ignoring you . know any of the negative consequences of . doing either one of these all we're . really focusing on is efficiency so . whichever one's safer that kind of thing . this isn't the place for that discussion . we're literally just talking about which . is more efficient now there are two . different scenarios i want to talk about . to answer this question because of . course the answer is it depends and so . the first scenario we're going downhill . we're starting at the top of a hill and . then we're going to stay on this simple . straight path to the bottom of that hill . and then we're stopping there at the . bottom and in this scenario the more . efficient thing to do is to leave it in . gear and the reason why is because when . you leave it in gear and you take your . foot off the gas and you're just using . engine braking your engine no longer . injects fuel so you're using absolutely. no fuel as you go down the only thing . that's keeping you going is gravity and . inertia and your engine is actually . working against you to slow the vehicle . down so the engine is rotating yes but . it's rotating because the wheels which. are connected to the transmission are . forcing it to and it's eventually going . to slow the vehicle down to a stop if . you run out of hill and so just a quick . demonstration of that i've got a you . know video that's showing my live fuel . economy and if i let my foot off the gas. completely you can see it goes to ninety . nine nine which is the maximum it'll . ever read and that's because the fuel . injectors are shut off if i put my foot . on the throttle it'll go back down and . you can see that it's using fuel so the . instant i touched the throttle you can . see it is using fuel but if i let off. completely. it goes to ninety nine nine quits . injecting fuel and you can see that . that's an efficient way to run now if i . do put it in neutral it now has to take . care of that engine and use fuel to keep . it running so you can see that if i go . slow enough so now i'm doing 25 and it . eighty miles per gallon rather than 99 . if i were to put it in gear so let me . put it in gear still staying at 25 and . you can see it goes up to 99 nine . because it is now shut off that fuel . injection so to keep it idling it has to . use some fuel and so that results in us . seeing you know that fuel economy of 90 . miles per gallon or whatever it may be . it's obviously not using much fuel it . doesn't take much fuel to keep an engine . idling but if you're traveling really . slow and you can see that will of course . start to drop because the amount of fuel . you're using relative to how quickly . you're moving has increased okay so our . second scenario is there possibly a . scenario where coasting and neutral . would be more efficient and there. absolutely is so let's say you start at . the top of a hill and then you come down . quite a bit and then you go up another . smaller hill and then you go down and . then you go back up another smaller hill . and then you go down and you back up . another smaller hill and so on until you . finally reach your destination well if . you put it in neutral as you're coming . down that first big hill you're going to . gain a lot more speed than if you were . to leave it in gear so by leaving it in . gear yes you won't use any fuel but then . you'll get to the bottom of that hill . and you'll have to use fuel to work your . way up over it versus if you were in the . car that was coasting in neutral has now . reached a high enough speed i mean this . is basically how rollercoasters work . they have enough gravity to get over . that next smaller hill that they go on . and so the same thing applies in this . scenario with your car you can leave it . in neutral you're not using much fuel . and you're able to use all of that . momentum from the first hill to go over . the second one and the third one and the . fourth one and so on so in scenarios . where you're going down a steep hill and . you know you want to get over the hill . in front of you using the least amount . of fuel coasting a neutral can allow you . to build more speed and therefore do it . now you might exceed the speed limit . it's not exactly safe to be in gear . because you have less control of your . acceleration obviously so there are . reasons why you don't want to do it but . from an efficiency standpoint it would . be more efficient to just coast in . neutral in that scenario and roll over . those smaller hills rather than use the . engine to you know put it in gear . and drive up those smaller hills which . of course will use a decent amount of . fuel but as you can see here you know . we're just kind of coasting down at . around 30 30 so miles an hour the a/c is . on so it's you know also running the . engine for the air conditioning and . we're getting about 85 miles per gallon . of course if i were to then stick it in . third gear and release the throttle . completely you can see you know it can . continue to run that air conditioning . even without using any fuel simply by . using the inertia of the vehicle to help . rotate that engine and we're getting you . know infinite miles per gallon because . we're not using any fuel so as always to . answer the question you know these kind . of hypothetical questions which one is . more efficient the answer is always it . depends if you guys have any questions . or comments feel free to leave them . below thanks for watching . you. .
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