Why YSK: People seem to, on average, think that a car takes a lot of fuel to start up. In reality, it takes on the order of a few millilitres of fuel to start an engine. That means if your car isn’t equipped with an automatic start/stop system to stop your engine instead of idling, it saves fuel to turn off your engine and start it back up when you need it.

Caveat: air conditioning and radio might not work with the engine turned off.

Scenarios where this might be useful include waiting for trains to pass at rail crossings, waiting for food at drive-throughs, dropping off or picking people up on the side of the road when they need to load stuff, etc. May not be a good idea to use this while waiting at a red light because starting the engine does take time which would annoy drivers behind you when the light turns green.

Some cars are equipped with systems that will automatically stop the engine when you are idling for a while (e.g. waiting for a red light). If yours is, then manually turning off your engine will probably result in reduced fuel savings compared to just relying on the car to do it for you.

  • boonhet@lemm.eeEnglish
    6·
    1 year ago

    Caveat: For cars not equipped with automatic start/stop, the starter and possibly the battery might not be specced for it so it could cause additional wear. Cars with start/stop systems often assist the process with precise camshaft position measurements and the ability to squirt fuel pretty much right away so the starter doesn’t need to do as much work.

    Also don’t do it with a cold engine - it’s better to get the oil up to temp faster, it’ll also reduce fuel consumption as the engine heats up.

    • LinkOpensChest.wav@lemmy.oneEnglish
      2·
      1 year ago

      I walk, cycle, or longboard places whenever possible, and when these automatic cars started coming out, I thought they were manually starting and stopping their cars at each intersection. It really tripped me out.

    • Hildegarde@lemmy.worldEnglish
      1·
      1 year ago

      Cars with start/stop systems often assist the process with precise camshaft position measurements and the ability to squirt fuel pretty much right away so the starter doesn’t need to do as much work.

      I always wondered why hybrids could start their engines instantaneously, when many conventional cars couldn’t. This is why, isn’t it?

      • Favor@beehaw.orgEnglish
        2·
        1 year ago

        I can’t speak for other cars, but my Prius uses the electric assist motor as the starter motor as well. Compared to a regular ICE car that’s a massively stronger electric motor than average starting a smaller than average engine.

        My favorite thing about it though is I have the longer hatchback model and if you replace one of the back seats you can fully lie down for car camping. What about the heat you may ask? I can just leave the AC on overnight, the car will start up and use the engine like a generator to recharge the battery then turn back off autonomously. I always keep some spare gas in case but I’m always shocked how little it uses.

      • The_iceman_cometh@partizle.comEnglish
        1·
        1 year ago

        This is why, isn’t it?

        Regular old cars use weak starter motors from the 12V battery. They’ve gotten better, but it’s still just a small part used only to start the car, so it only turns over the engine fast enough to get it going.

        A car like a Prius will put the car’s big, beefy generator in “reverse” to start the motor at whatever RPM the computer wants it at, and since it has abundant power from the synergy drive batteries, it can start the engine at whatever RPM the computer deems appropriate.

    • mikerussell@lemmy.worldEnglish
      0·
      1 year ago

      Thanks for reminding everyone of this. The gas savings over time will probably end up being the same, or less, than a starter on an older vehicle. Of course, if you’re not planning on keeping the vehicle until it dies, this is less of an issue for you.

      • LUHG@lemmy.worldEnglish
        0·
        1 year ago

        It’s the battery prematurely dying that’s also an issue. Especially if the battery needs coding to the car. Could be a £300+ job. That’s a lot of fuel that’d need to be saved to be close to worth it.

        It’s all about emission testing anyway. Keel start stop off.

        • 𝕾𝖕𝖎𝖈𝖞 𝕿𝖚𝖓𝖆@lemmy.worldEnglish
          1·
          1 year ago

          Wait, CODING? Are you serious? I can understand this with EVs, but for a standard 12 volt battery? This sounds more like a thing they do to keep you from doing your own work and allowing shops to charge more flag time for what should be a 10 minute job. Replacing a dead battery is one of the simplest jobs you can do. The hardest part of a battery swap should be finding your 10mm socket.