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Yeah, Right.

  1. Jan 15, 2009 #1
    I got this in my school FYI email:

    I think my engine and transmission oil needs more time than that to heat up and work properly. Also, suddenly driving off with a cold engine block is a good way to develop cracks in the cylinder walls - which is why you don't just pull the throttle all the way out on an airplane. You gradually reduce it back to idle.

    Brewski, give me your expert advice.
     
  2. jcsd
  3. Jan 15, 2009 #2
    Warming up the engine block will take a lot longer than 2 minutes if you're just idling, it is quiet a lot of metal. Also the difference between idling and driving of carefully is not that big. I don't idle but drive gently in the first 10 minutes and haven't ever experienced any cracked cylinder walls, despite some less gently driving after 10 minutes passed.
     
  4. Jan 15, 2009 #3
    30 seconds doesn't seem like a long enough time. A guy I know fixes cars for a living, and since the weather turned bitter up here (-20s at night) they've seen an influx if cars with power steering problems caused by, in his opinion, not letting the car warm up long enough. Same thing happened to me last winter.
     
  5. Jan 15, 2009 #4

    Gokul43201

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    30 seconds is just about long enough to run the engine oil through the system, I guess. My owner's manual (Honda Accord) suggested something along the lines of waiting 20-30s, and drive "gently" for the first 5 minutes, if I recall correctly. That's what I've always done.

    I've had this car for 6 years (in the mid-west and NE), and never once idled for a minute before taking off. So far, not a single problem with the engine, and I still get over 30mpg from a car with 160K miles on it.
     
  6. Jan 15, 2009 #5

    Ivan Seeking

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    The problem that we have is that our driveway is fairly steep and long, so there is no way to avoid loading the engine.

    The real test is whether you get 180k or 300k out of a Honda.
     
  7. Jan 15, 2009 #6

    turbo

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    With a push-rod type engine, I always let the engine idle until the lifters are pumped up (tapping noise stops), then drive away gently. Never any problems, and my cars routinely last 200K miles or so, though the road-salt eats up the bodies before I can wear them out mechanically, so I'll never know what the engine/transmission will last. I sold my last Pathfinder (lightly used) at the age of 17 years with about 190K on the odometer. The buyer did extensive body work, and two years later, he was still driving it.
     
  8. Jan 15, 2009 #7

    mgb_phys

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    If you have a modern engine management system it will do this for you.
    My subaru annoyingly revs to about 3500 for a couple of seconds about 10secs after I start if it is idling - I think it is monitoring the NOx in the exhaust and trying to get the combustion up to temperature.
    Trouble is this is just when I'm under my neighbors window - she thinks I'm doing it to annoy her!
     
  9. Jan 15, 2009 #8
    My auto manual also says not to idle more then a minute. But I need heat, so I warm it up just a tad, say 5 minutes. Just so my heater is kicking out a bit of warmth.
     
  10. Jan 15, 2009 #9
    I would say it is more about the ability of the oil to do it's job. A cold engine always wears more than a warm one. I lean towards letting it warm up at an idle.
     
  11. Jan 15, 2009 #10

    brewnog

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    Ha, my "expert advice" would be that 30 seconds is more than adequate. I get in and drive away, unless the car needs de-icing (in which case I let the engine run, with all the lights and demisters on, and that's more to try and get heat into the cockpit!).

    However, you should then drive the car gently (avoid full throttle, and limit your revs) until the water is showing a reasonable temperature. I wait until the water temperature is at around 60°C before giving it stick, and 80°C before thrashing it.

    Far more damage is done by thrashing a cold engine than by not idling an engine at all, and then driving normally.

    The car I have at the moment never gets warm if you only let it idle, it has to be driven to get any heat into the thing. While it's idling away after starting, the oil is cold, the oil pressure is low, and it's constantly wearing away bits of metal.

    Ivan, unless you blat up your drive at 70mph, I wouldn't worry about loading the engine excessively before it's warm.
     
  12. Jan 15, 2009 #11

    Ivan Seeking

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    In that case I'm probably okay... but Tsu is another story... esp with her V6 Solara. :grumpy:
     
  13. Jan 15, 2009 #12
    Yes! That's my reason too! :biggrin:
     
  14. Jan 15, 2009 #13

    dlgoff

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    Doesn't seem they are worried about your saving your engine. Maybe you should reply and ask if they are willing to repair your engine when it dies.
     
  15. Jan 15, 2009 #14

    Gokul43201

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    From what folks are saying so far, it seems you don't do much harm to your engine.

    Clearly you save time, but I doubt you save much money or emissions. I would imagine you'd get a significantly lower mileage over the first few miles driven with a cold engine (compared to when it's warmed up). But that's just a guess - I have no idea what the numbers would be.
     
  16. Jan 15, 2009 #15

    wolram

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    I think air cooled engines (aircraft) are a different kettle of fish, fast heating and cooling can cause cracks, look to the vw engine, finding a twin port head with no cracks is a rarity.
     
  17. Jan 15, 2009 #16

    turbo

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    Part of that syndrome may be due to the fact that the VW bug with the weight over the driven wheels was great in snow, and was abused in some pretty severe climates.
     
  18. Jan 15, 2009 #17

    wolram

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    I have rebuilt hundreds of these engines, the only time i have come across one without cracks in the cylinder heads, the owners have allowed the engine to warm up and cool down slowly, plus i would not guarantee the engine unless the heads were re torqued, i used to run an engine for an hour and re torqued the heads, it was up to the owner to get them re done before 500 miles.
     
  19. Jan 15, 2009 #18

    JasonRox

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    The most I've ever waited to start driving my car is about 3 seconds. I drive hard too.

    I have to wait 2 to 3 minutes before I start riding my scooter though, and I have to wait 2 to 3 minutes before killing the engine too.
     
  20. Jan 16, 2009 #19
    Note to self: Don't buy used cars from Jason.
     
  21. Jan 16, 2009 #20

    Ivan Seeking

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    Go to this guy [profanity]
    https://www.youtube.com/watch?v=uTvwwDnrQL8
     
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