# 10 second rule



## weedygarden (Apr 27, 2011)

A number of years ago I heard that about 1/4 of the gas consumed in America is while vehicles are idle. Think of stop lights, drive throughs, etc. The same story said that if you need to wait more than 10 seconds, it will save you gas to turn your vehicle off and restart when ready to move.

I realize that air conditioning and heat are factors sometimes when leaving a vehicle running while idle, but I have found that there are many more opportunities to turn my car off and restart than I had realized.

I call it the 10 second rule and would love to see a national campaign about this.


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## Meerkat (May 31, 2011)

I figure more on the 3 minute rule.After that I turn off,but anythign sooner will only put more into the air and take more gas to restart,could be wrong,but thats what the Shell Answer Man said years ago.


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## Sentry18 (Aug 5, 2012)

I was told once that for short periods of time (1-2 minutes) you burn more gas restarting the car than you would have just letting it idle. But I am not a mechanic and I don't play one on tv, nor did I stay in a Holiday Inn Express last night. So we will have to wait for someone more knowledgable to come along.


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## The_Blob (Dec 24, 2008)

Meerkat said:


> I figure more on the 3 minute rule.After that I turn off,but anythign sooner will only put more into the air and take more gas to restart,could be wrong,but thats what the Shell Answer Man said years ago.





Sentry18 said:


> I was told once that for short periods of time (1-2 minutes) you burn more gas restarting the car than you would have just letting it idle. But I am not a mechanic and I don't play one on tv, nor did I stay in a Holiday Inn Express last night. So we will have to wait for someone more knowledgable to come along.


Yes, that would be correct. Internal combustion engines can get as little as

*1/10* their rated mpg until reaching operating temperature, and THAT is the primary determining factor in differentiating 'city mpg' vs 'highway mpg', urban drivers tend to not have to travel as far as their more rural counterparts, thereby not getting their engines 'warmed up'.


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## UncleJoe (Jan 11, 2009)

Something else to consider is the wear and tear on your starter. If you're turning your car off at every red light you could be using that starter 10-20 times as often. I would have to weigh the cost of replacing the started more often with the gas savings. I don't know what the average starter costs but for my Cummins diesel that starter is over $200. And that's with me installing it. If you need someone else to do the labor, add another $200. Over the long run I don't know if restarting at every light would save me anything. :dunno:


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## Tirediron (Jul 12, 2010)

Some un learned greeny must have come up with the 10 second rule cause that would effectively double idle time fuel consumption and quadripple the carbon foot print. the wear on the starter has been mentioned as well as the engine temerature. temperature also has to do with the mode that the engine runs in so if it never got the O2 sensor up to closed loop mode the engine would cold start every time and spray excess fuel washing the cylinder walls and cause premature engine death. 
the automotive starting / charging system is not an efficient energy converter either so more loss. 

in traffic leave it idle unless it is obvious that the stoppage will exceed 10 minutes. 
If you want to save fuel get the stupid salesmen to stop telling new diesel truck owners to idle their truck excessively like more than 5 minutes at a parked situation, but these shut downs need to be after a cool out period if the engine has been underload. 

And I seriously doubt that 1/4 of the gas burned is wasted by idling engines, maybe 1/4 of the gas burned in a big city when delivery trucks and taxi's ran from the start of their shift until the end but once the engine is up to temp most of these operators shut their engine off for longer sitting periods.


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## cnsper (Sep 20, 2012)

I only shut it off at traffic accidents and train crossings.


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## Immolatus (Feb 20, 2011)

I wont purport to know the details, but I will say that in Europe where the cars get much better mileage, EVERY car I have ever rented over there (four, not a large sample size) automatically shuts off at idle after a few seconds (like 3). So I think there must be something to it, no? The last car I had in August shut off almost instantly idling at a stop, and would start as soon as you press the clutch, and if not for the engine noise you wouldnt even know it happened.


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## Tirediron (Jul 12, 2010)

Big difference in a system designed to be shut down & restarted than a normaly run system pressed into on off service. the euro stuff is shut off with the ecm still powered so the re start is more like a zero rpm idle as opposed to a reboot with a starting fuel cycle. But does the fuel saved make up for the extra cost to overall component life? many EPA "improvements" result in more pollution in the big picture. Lots of people don't do big picture.


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## partdeux (Aug 3, 2011)

I work for an Auto Mfg OEM in product development. While my expertise is not in engines, I have some general knowledge WRT the technology.

Systems that are designed around idle shutdown, have upgraded starters and batteries. Turns out the batteries take a huge hit using the technology.

Now, for the good part, in real world application they save very little fuel. Mazda did a study and they came up with a IRC ridiculous .2%. The OEM's have convinced themselves there's a real and reportable savings, with the EPA being complicit in allowing the driving cycle to take advantage of the technology. BUT, the average consumer HATES the technology, and it further drives up the cost of a new vehicle.

As auto's have become more and more fuel efficient, there's a huge rate of diminishing return on new savings. Save 10% on a 12mpg vehicle and you'll have something. Save 10% on a 36mpg vehicle and you'll gain virtually nothing in savings. Save 10% on a 50mpg vehicle, and you'll have a payback period that will exceed your car life.


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## LincTex (Apr 1, 2011)

Tirediron said:


> Temperature also has to do with the mode that the engine runs in so if it never got the O2 sensor up to closed loop mode
> 
> the engine would cold start every time and spray excess fuel washing the cylinder walls and cause premature engine death.


The new HEGO's warm up really fast. Less than 10 seconds and they are sending info to the ECM.

Besides, the ACT and IAT sensors as well as ECT sensor will tell the computer the engine is already warm, so there would be no "cold" start mode, so no cylinder wash.

Besides, have you ever looked at injector duration times on a scan tool? "Cold start" is not much more duration than a normal run, so there is NEVER any "cylinder wash" on a modern ECM controlled engine.

When the engine is warm, the injector duration during "start" is exactly the same as during "run", so there is never any "rich" period during a warm start.


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## CulexPipiens (Nov 17, 2010)

I had a car, Civic Hybrid, awhile back, that did shut off automatically. Once it was warmed up this technology would kick in. Only catch is it sucks in stop and go traffic as you don't normally stop long enough to make it useful, nor do you go fast enough to make it "kick in" next time you stop. Otherwise it worked fine and hever impacted the car. As stated, the starter motor is designed to handle this. Basically when I took my foot off the brake, and before I could get it to the gas pedal, the car was already back at idle. On current cars I've heard (don't know the accuracy though) that the technology and better starter motor adds about $300 to the cost of the vehicle. Over, let's say, 100,000 miles, that's .003 cents per mile. Or, look at your MPGs, let's say 20, which would be 5,000 gallons of gas for 100,000 miles. If you're saving just 2% that's 100 gallons. @ $3.50 per gallon, that's $350. So it would be a very modest cost savings. As also stated, lower mileage saves more, higher mileage saves less.


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## Tirediron (Jul 12, 2010)

LincTex said:


> The new HEGO's warm up really fast. Less than 10 seconds and they are sending info to the ECM.
> 
> Besides, the ACT and IAT sensors as well as ECT sensor will tell the computer the engine is already warm, so there would be no "cold" start mode, so no cylinder wash.
> 
> ...


if by modern you mean OBD 3 and up ok, the early stuff did wash, seen lots of evidence, but since this is aimed a commuter traffic some times in cold weather how would the ecm learn to get to an optimum run set up for the particular engine. shut down and re start in an engine specificly designed for it also wears valve guides / stems due to hot oil run off, but if you want to shut your engine off at stop lights be my guest,


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## partdeux (Aug 3, 2011)

CulexPipiens said:


> I had a car, Civic Hybrid, awhile back, that did shut off automatically. Once it was warmed up this technology would kick in. Only catch is it sucks in stop and go traffic as you don't normally stop long enough to make it useful, nor do you go fast enough to make it "kick in" next time you stop. Otherwise it worked fine and hever impacted the car. As stated, the starter motor is designed to handle this. Basically when I took my foot off the brake, and before I could get it to the gas pedal, the car was already back at idle. On current cars I've heard (don't know the accuracy though) that the technology and better starter motor adds about $300 to the cost of the vehicle. Over, let's say, 100,000 miles, that's .003 cents per mile. Or, look at your MPGs, let's say 20, which would be 5,000 gallons of gas for 100,000 miles. If you're saving just 2% that's 100 gallons. @ $3.50 per gallon, that's $350. So it would be a very modest cost savings. As also stated, lower mileage saves more, higher mileage saves less.


It adds more than that in cost, sale price IRC is in the $2,500 range.

Using your example, for 100,000 miles, at 30mpg and $3.50 per gallon, you will save $1,061. at 50mpg, I could make the argument that you will no longer save the same 3mpg, but maybe 2 (or less). Now you're only saving $259.

But, keep in mind, the Mazda study said real world savings is almost unmeasurable, it's that small.


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## LincTex (Apr 1, 2011)

Tirediron said:


> if by modern you mean OBD 3 and up ok,
> 
> shut down and re start in an engine specificly designed for it also wears valve guides / stems due to hot oil run off,


Nope, OBD II, specifically the '86 and up Mustang/T-bird, etc computers. I know these systems very well, have played with EFI mustangs for ages.

I don't see your argument for valve guide wear. I have seen no evidence at all to support that claim. I have had numerous 5.0 liter Ford engines go over 200,000 miles without any serious guide wear. Besides, all modern engine use positive valve guide seals on the intake valves, which essentially "wipes" the oil from the stem anyway. They don't wear. ALSO, you will never get any "hot oil run off" from any valve guides (intake or exhaust) due to umbrella-style valve guide seals preventing any oil flow over the exposed valve stem in the first place.

Your arguments don't hold any water at all, when dealing with engines less than 25 years old.


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## CulexPipiens (Nov 17, 2010)

partdeux said:


> It adds more than that in cost, sale price IRC is in the $2,500 range.
> 
> Using your example, for 100,000 miles, at 30mpg and $3.50 per gallon, you will save $1,061. at 50mpg, I could make the argument that you will no longer save the same 3mpg, but maybe 2 (or less). Now you're only saving $259.
> 
> But, keep in mind, the Mazda study said real world savings is almost unmeasurable, it's that small.


Shouldn't the savings go down, not up as mileage increases?

30mpgs would yield 3333 gallons for 100k miles. If you can save 2% of that, then that's 67 less gallons you'd need. At $3.50 per gallon you're saving about $234, not over $1000.

Ford has the autostop for $295 extra on the Fusion as an option. http://green.autoblog.com/2012/09/16/ford-s-auto-stop-start-offers-hope-to-foot-heavy-drivers/

"For the 59 percent who are not willing to slow down to save on gasoline consumption, Ford asks how about stop-start technology? The 2013 Ford Fusion is offering EcoBoost with Auto Start-Stop technology, along with EcoBoost only and hybrid and plug-in hybrid offerings. For those taking the survey, they're willing to pay more upfront for green products to save money over time, and Auto Start-Stop adds $295 to the purchase price."


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## Tirediron (Jul 12, 2010)

LincTex said:


> Nope, OBD II, specifically the '86 and up Mustang/T-bird, etc computers. I know these systems very well, have played with EFI mustangs for ages.
> 
> I don't see your argument for valve guide wear. I have seen no evidence at all to support that claim. I have had numerous 5.0 liter Ford engines go over 200,000 miles without any serious guide wear. Besides, all modern engine use positive valve guide seals on the intake valves, which essentially "wipes" the oil from the stem anyway. They don't wear. ALSO, you will never get any "hot oil run off" from any valve guides (intake or exhaust) due to umbrella-style valve guide seals preventing any oil flow over the exposed valve stem in the first place.
> 
> Your arguments don't hold any water at all, when dealing with engines less than 25 years old.


Alright so what lubes the valve stem ?? how do you know the service cycles of the engine that you base you claims on, and I have seen numerous ford pickup engine failures due in part to fueling issues, but the climate is way different here, a warm day here is a cold day in Texas. Like I said before if you believe that short shutdown cycles are profitable go to it. I can't see how the additional cost in starting system life would ever be recovered.


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## ZoomZoom (Dec 18, 2009)

For extended idles (e.g. a train crossing), I just pop it in neutral to take the load off the engine. Sitting at idle under no load doesn't burn much.


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## LincTex (Apr 1, 2011)

Tirediron said:


> Alright so what lubes the valve stem??


I guess it just doesn't take much oil to keep the guide lubricated. I did a google search for "positive valve stem seals" to go looking for answers. Here is a good article, but it is too long to post the whole thing. You'll have to go read it all yourself.

http://www.enginebuildermag.com/Article/2522/valve_stem_seals_materialsdesigns.aspx

_7/1/1998
Click on a thumbnail to see the full-size image
Valve Stem Seals Materials and Designs By Larry Carley

In the mid-1980s, positive valve stem seals made of fluoroelastomer materials (FKM and Viton) began to appear in import and domestic overhead cam engines. Fluoroelastomer seals cost roughly 12 times as much as nitrile, but have a temperature range of -5º to 450º F, making them one of the best high-temperature seals available.......

Seal design
Valve stem oil seals come in two basic types - umbrella seals and positive seals. Used mostly on older pushrod engines, umbrella or deflector style seals (which also include O-rings) are installed on the valve stem and ride the stem up and down as the valve opens and closes.

An umbrella seal controls the amount of lubrication the valve guide receives by deflecting oil splash away from the guide. An O-ring does the same thing by preventing oil from flowing down the valve stem into the guide. Umbrella seals are a simple and effective design, and are easy to install. But they do not provide the same degree of oil control as positive seals.

Positive seals are used on most late model engines for two reasons: emissions control and oil control. A positive valve stem seal provides a tighter seal which reduces the amount of oil that enters the guides. This minimizes oil consumption and hydrocarbon emissions, and also helps to keep intake vacuum high for better idle quality (air being sucked past worn valve guides and seals can cause lean misfire and a rough idle).

A positive seal is also needed in most overhead cam engines to prevent oil from flooding the guides. An umbrella seal cannot handle the amount of oil that's found in most OHC heads.

Unlike an umbrella seal, a positive seal does not move. *It is pressed in place on the end of the valve guide and wipes the oil off the valve stem as the stem moves up and down.* The seal does not actually make direct contact with the stem but rides on a thin film of oil creating a hydrodynamic seal. This allows a small amount of oil to slip past the seal to lubricate the guide. For this reason, a precise fit is extremely important with a positive seal to get accurate oil metering....._



ZoomZoom said:


> For extended idles (e.g. a train crossing), I just pop it in neutral to take the load off the engine. Sitting at idle under no load doesn't burn much.


My uncle put one of these in his F-150 in Houston, he says shifting into neutral at any stop light shows an immediate 5 MPG increase. 
http://www.andybrain.com/archive/scangauge-review.htm


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## Tirediron (Jul 12, 2010)

Most of the junk that I see fail is probably close to the end of it's life cycle anyway. I still don't agree with 10 second shut downs even if the engine is designed for cycling, a longer period is required for it to pay off. shifting to neutral and a longer coast period comming up to stops. maybe turning the A/C off would help a lot more maybe don't make unnessicary trips and use carpooling. I will not be shutting my engine off in stop and go traffic anytime soon, although I don't spend much time at all in city traffic anyway.


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## partdeux (Aug 3, 2011)

CulexPipiens said:


> Shouldn't the savings go down, not up as mileage increases?
> 
> 30mpgs would yield 3333 gallons for 100k miles. If you can save 2% of that, then that's 67 less gallons you'd need. At $3.50 per gallon you're saving about $234, not over $1000.
> 
> Ford has the autostop for $295 extra on the Fusion as an option. http://green.autoblog.com/2012/09/16/ford-s-auto-stop-start-offers-hope-to-foot-heavy-drivers/


I'm shocked they are selling it for $295. The costs has to be much more than that.

Normal customers don't like the technology, Mazda reported the real world savings to be non existent. I think it's a dead end.


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## CulexPipiens (Nov 17, 2010)

Not sure. MINI claims it adds about $300 to the price also. They described it as a bit of programming in the computer and a beefier starter motor. I think cars that now have a "start" button instead of a "turn the key" pretty much already are starting the car for you so perhaps it comes down to how many times the starter motor is rated for starting your car??? Dunno. :dunno:


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