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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / November 2006avoiding cold starts
First, are these assumptions correct? (1) Starting a car when the engine is cold puts alot more stress on it than when it's already warm. (2) And the colder it is, the more stress. Because i've always assumed the above, I do the following, but I want to verify whether it's really worth it and doing any good...noone else that I know does this. If I know I"m going to cold-start and then drive to a destination that is only a short distance (less than 5 miles) and then a second destination a short time later, rather than go to the first destination and turn off the engine off right away (before it's reached full operating temps, at least based on the "thermometer" on the dash), I'll usually drive around a little bit more, or let the engine run for about more minutes, before turning it off........since I know i have to re-start it in less than an hour to go to my second destination....so tha when i re-start it the engine should still be warm. Also, in other cases, if after reaching the first destination with the engine not fully hot...., rather than turn it off, i'll just leave the car and let the engine run (if it's just a short stop over, like 5 minutes) and then go on to my 2nd destination. I'm wondering whether i'm doing any good by this. Modern engines with modern oils are way less sensible to cold starts. What you are doing does not do any noticeable good for your engine, and technically does not hurt either. It hurts your wallet and our ecology, though.  SignatureMishaA http://www.automotiveforums.com > First, are these assumptions correct? > (1) Starting a car when the engine is cold puts alot more stress on it [quoted text clipped - 21 lines] > > I'm wondering whether i'm doing any good by this. Define cold. Cold to me is anything below 85F. Below 50F and I don't go outside. > Define cold. > Cold to me is anything below 85F. Below 50F and I don't go outside. On the Canadian Prairies: 85F = Hot day. Stay in the shade. 50F = Might want a sweater on. 40F = Time for the jacket. 20F = Time to change the oil. Max 5W30, maybe 0W30. 0F = Getting a little chilly. Might want to warm the engine for two or three minutes before driving or it might cough and die. -20F = Plug in the block heater. Put on long underwear. Wear a hat. -40F = Some parents keep kids at home from school. The rest of us go to work. -50F = Can't talk outside. Your words freeze and fall to the ground, and in the spring everyone can hear what you said about them when those words melt. -60F = Smoke freezes in the chimney and the furnace fumes back up into the house. Got to climb up on the roof and poke a long stick down through the frozen smoke, turn the heat way up and burn the rest of it out. -70F = Can't drive at night. The headlight beams freeze to anything they hit and immobilize the vehicle. Have to turn off the lights to get moving again. Dan It's better to let any engine warm up as much as possible, but leaving the car running (unless it is occupied) is a great invitation for car thieves. Many people have gone to 7-11 to get coffee on the way to work and left their cars running while in the store only to have it disappear while getting their coffee. Roy > First, are these assumptions correct? > (1) Starting a car when the engine is cold puts alot more stress on it [quoted text clipped - 21 lines] > > I'm wondering whether i'm doing any good by this. > First, are these assumptions correct? > (1) Starting a car when the engine is cold puts alot more stress on it > than when it's already warm. > (2) And the colder it is, the more stress. I would dispute that it puts "a lot" more stress on it. Cold starts with modern oils of the correct grade for the climate you're in are really a non-issue. Yeah, a modern engine may piston-slap like a diesel when its cold and sound very different than when its hot (unlike older engines with different piston alloys and designs that traded efficiency for quiet when cold,) but that's a completely harmless sound. It would be far more harmful if the pistons bound in the bore when the engine was fully heated up. > Also, in other cases, if after reaching the first destination with the > engine not fully hot...., rather than turn it off, i'll just leave the > car and let the engine run (if it's just a short stop over, like 5 > minutes) and then go on to my 2nd destination. > > I'm wondering whether i'm doing any good by this. You're probably doing HARM through excessive fuel dilution into the lubricating oil. > You're probably doing HARM through excessive fuel dilution into the > lubricating oil. Interesting....I was reading in the past few years that idling doesn't hurt the engine any more than driving does....but i think a LONG time ago I used to hear that it's not good to idle too "long" (an hour?). One slightly related (to my original question) thing I heard last year: If your going to let you car sit parked (off) for a long time (weeks??), you should NOT 't drive a short distance and then turn the engine off before the long parking duration....You should drive it until it's fully warmed up....supposedly the condensation in the engine would remain there and cause rust if you don't fully warm it before turning it off and letting it sit.......true? > > You're probably doing HARM through excessive fuel dilution into the > > lubricating oil. > > Interesting....I was reading in the past few years that idling doesn't > hurt the engine any more than driving does....but i think a LONG time > ago I used to hear that it's not good to idle too "long" (an hour?). Must have been when carburetors were the norm. I can't imagine that a modern fuel-injected and electronically controlled engine would have problems with idling for long periods of time. > One slightly related (to my original question) thing I heard last > year: If your going to let you car sit parked (off) for a long time [quoted text clipped - 3 lines] > would remain there and cause rust if you don't fully warm it before > turning it off and letting it sit.......true? Modern motor oil is probably better in handling all this stuff. Many (if not most) engines these days are aluminum. I've never had an oil analysis with any appreciable amount of moisture, even when taken after a short drive. >>You're probably doing HARM through excessive fuel dilution into the >>lubricating oil. > > Interesting....I was reading in the past few years that idling doesn't > hurt the engine any more than driving does....but i think a LONG time > ago I used to hear that it's not good to idle too "long" (an hour?). The problem isn't idling, its idling when cold. Idling will *never* bring the oil up to full operating temp, even if the coolant gets there, and its the oil that really needs to be heated to drive out absorbed fuel and water vapors. > One slightly related (to my original question) thing I heard last > year: If your going to let you car sit parked (off) for a long time [quoted text clipped - 3 lines] > would remain there and cause rust if you don't fully warm it before > turning it off and letting it sit.......true? Its not that it causes rust, its that it causes acid formation in the oil. But yes, its generally true. An occasional short cold trip really isn't going to do any harm because the buffers in oils can handle the acids just fine. But doing that sort of thing on a daily basis will eventually overwhelm the oil and the total base number will decline, meaning the oil is becoming acidic. I borrowed and electricity consumption meter from the public library and put some of the numbers I got in a file a www.ag384bn.bravehost.com/hydro.htp including the block heater on my car. You can find some vauge references to fuel savings using a block heater on the Internet but no hard data. It would be nice to have. My impression is that an engine idling over any time without a load on it will shake itself silly but an engine with a load on it won't shake as much. Just an unrpoven theory of mine. My manual says not to idle more than 30 min. Here in Ottawa where winters get pretty cold remote starters are popular just to warm up the car so people have a nice warm car to get into, nothing to do with the engine, everything to do with creature comfort. > My impression is that an engine idling over any time without a load on > it will shake itself silly but an engine with a load on it won't shake > as much. Uh.... no. The engine is just as balanced at idle as it is under load. Thanks for the replies. I've actually never left my car running unattended, and i never planned to (what i meant at the end of my original message was that i might let it run while stopping at a destination, but not leaving it alone (like more than 10 feet away from me). Actually, the only time i let it run unattended was in an long-term airport parking lot a few weeks ago, when I flew to Europe for one week, and left the car running in the parking lot for a week, because i heard the weather was gonna be very cold....and didn't want to start it when i got back....didn't seem to cause any problems, though gas was almost empty. (just kidding) > First, are these assumptions correct? > (1) Starting a car when the engine is cold puts alot more stress on it [quoted text clipped - 21 lines] > > I'm wondering whether i'm doing any good by this. Depending on where you are leaving the engine idling may be illegal. It is also a very poor idea since many of the insurance companies have it buried in the fine print that leaving the keys in the vehicle means they don't have to cover it in the event of loss/theft. It is also not required with modern vehicles and oils. SignatureSteve W. Near Cooperstown, New York >"... I'm wondering whether i'm doing any good by this." Your Owner's Manual will probably say you are in the severe driving condition catagory. As far as oil change intervals, it means follow the RECOMMENDED o.c.i. If I were in this situation, and using my favorite synthetic engine lubricant, I have the option and confidence to follow what it claims on the lable. |
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