5 ms·

Think about what is required to turn the engine over and prevent stalling. -When the clutch is engaged whilst going down hill the wheels turn the engine. No F

• nostrademons 10y ago
  It's not the fuel required by the engine, it's the engine braking. Going down a hill with clutch disengaged, the Accord would accelerate. With clutch engaged, it would slightly decelerate. That's fuel that the engine doesn't need to burn to accelerate it back up to cruising speed. Ditto when coasting to a stoplight - with clutch disengaged (or in neutral), it would coast for a longer distance, which - if you're careful and know your vehicle - means you can let up on the gas a lot sooner.
  • henrikschroder 10y ago
    Anecdotal, but I did some tests in my previous car (a 2014 Mercedes, automatic) and it coasted really, really, really well. In drive, downhill, on the freeway, feet off all pedals, it would accelerate as much as if I put it in neutral, so I think its software and transmission allowed it to perform as good as a manual in that situation. Not calling you out specifically, but a lot of people arguing for manual transmissions in this thread seem to base their experiences on ~10 year old cars or older, and weirdly assuming that nothing has happened since, that software and technology in cars has been magically frozen in time, despite enormous incentives for car manufacturers to improve it.
    • smileysteve 10y ago
      Automatics don't engine brake the same way, the torque converter is only fully engaged when it has some pressure buildup, so it will slip (and not maintain fuel cut) when coasting whenever the wheel speed won't maintain the pressure. To test, watch your rpm when you left off the gas, if it drops to ~750-1000 rpm, your torque converter is slipping (as designed) and not maintaining fuel cut. To agree with you, I think the comments in this thread started from a manual transmission standpoint and then everybody thought it applied to automatics.
      • fnj 10y ago
        It's not that simple, since everybody has had lockup torque converters (based on a computer-controlled clutch) for a long time now. As long as the TC is locked up, you have full engine braking. As you slow, it eventually drops out of lockup, you see the rpm drop to idle or close to it, and you feel the engine braking diminish (though you do still have a small amount, as the the transmission does have pumping and drag losses).
  • Retric 10y ago
    No free lunch. In a manual you are burning fuel when the clutch is disengaged to keep the engine turning over. With the engine engaged you steal from momentum which lowers fuel use. The mid point of keeping the engine engaged and adding enough fuel to reach your desired stopping point once the RPM enters the same range as an idling engine is actually most efficient.
  • ubercore 10y ago
    I'm pretty far out of my element here, but as I understand even that isn't universal. BMW's Valvetronic for instance doesn't engine break the same way as other engines, because they don't have a throttle valve and don't have a vacuum outside the intake valves: https://www.youtube.com/watch?v=DKfcV7hITYI https://www.youtube.com/watch?v=DKfcV7hITYI
• IshKebab 10y ago
  True, but the amounts of fuel needed for idling is minuscule.
• rascul 10y ago
  carburetor (American and Canadian spelling), carburator, carburettor, or carburetter (Commonwealth spelling) https://en.wikipedia.org/wiki/Carburetor https://en.wikipedia.org/wiki/Carburetor