Hi JC,

Not trying to fuel the debate a whole lot more, but I just can't help myself!

We've discussed the hazards and issues regarding running an engine under the rated operating temperature. Can you enlighten us as to the damages caused by lightly/moderately loading an engine that's below operating temperatures? It would certainly prevent the engine from operating long while cold, which is certainly helpful...but how exactly are you causing harm to the engine?

I know WOT runs can be damaging to any engine when cold because the typically aluminum pistons heat and expand faster than the iron bore and can cause scuffing, but I have never heard anyone make the claim that running an engine moderately can cause the same problem. Furthermore these engines benefit from piston cooling jets that will assist keeping the pistons near the same temperature as the rest of the block.

Even when cold maximum oil pressure is generated at the heads within seconds, although admittedly slower than when the engine is warm. Generally by the time the engine is started, put into gear, and throttle applied there is full oil pressure just about everywhere in the engine. This oil isn't just there, it's there and very thick, which would provide an increased level of protection against the harmful metal-to-metal contact that destroys engines.

So I'm not attempting to declare that you are wrong, just that I'd like a good explanation as to how moderate loading can hurt a cold engine. I've spoken with a couple of engineers that have indicated otherwise, and also the owners guide that was written meticulously by those who designed the engine do not insist that an idling period is beneficial before driving except during extreme cold.

How would this be different for the "flawed and less than almighty" gassers?
Thanks!

 

Tom, it's ok, I have theories based on my own experience and would never claim for a minute I'm always correct. I like chatting with knowledgeable guys like you because that's how we all learn, by thinking of all angles.

And I agree that lightly loaded shouldn't be an issue. Even light boost should not be an issue. Load technically should not cause a piston to 'wobble' on it's own. However, combine that with revs and that's where issues can arise I feel. Load forces the rings outward, creates friction (and heat) and evacuates oil from the cylinder walls. That reduces the protection you need for a piston that hasn't fully expanded and 'wobbles' at higher rpm's. How significant is this? Probably not a major issue but I just think getting some heat into the pistons before loading the rings can't be a bad thing. But really, to me revs are the killer and I high idle at 1200 rpm and I cannot imagine too many situations where you can easily drive around at less than that. But if you can, then likely that would be ok also.

That's my logic anyway. Feel free to riddle it with bullet holes! LOL

 

1,200 is perfectly OK when cold.
How do I know this is OK, well because Ford designed the engine to instantly jump up to 1,100 RPM as soon as it turns over when it's cold enough.
I don't think an extra 100 RPM is going to blow anything up.

For those who don't own a 6.7L, when I say instant, I mean it.

 

I sometimes spend a lot of time, like all day in my truck for work (more like waiting bored). Texas and the middle of summer, I spend a lot of time at idle.

 

I see what your point is, but there are two things that seem to contradict this IMHO. First of all consider most gasoline engines. They naturally operate at higher speeds during virtually all periods of their operation with the exception of the comparable idle of some larger displacement engines. Many of these engines get started up, run 2,000 RPMs at idle, thrown into gear, and driven down the road at 2,500-3,500 RPMs. Heck, many gassers like my '08 Dakota's 4.7L V8 at work won't even lock the torque converter until the engine comes up to temp. This thing sings along at nearly 3,000 RPMs on the highway when the engine is cold. Now if it were better to keep RPMs low during under-temperature operation would they not choose to lock the torque converter anyway to minimize piston ring damage? They don't, instead they prefer to run higher RPMs to get the engine up to temperature faster. I could say that this logic indicates that getting up to temp faster is the best case scenario, as this would directly contradict the idea of idling at low speed until it gets to temp.

Secondly consider how many millions of vehicles, gas and diesel, that are on the road, and of them how many get idled up to temp before taking off down the road. My second-to-last truck when I was driving commercially had an '06 Caterpillar C15 with 560,000 miles on it when I turned it in. In accordance with company preference, I used to start that thing up and throw it in gear after about 30 seconds just like most other company drivers.

I have yet to meet someone in person who has told me that they wore out an engine before junking a car. Of course it happens, but even vehicles that aren't driven conservatively are frequently junk long before the engine is done. I'd be willing to bet that most diesel engines in this nation are company-owned vehicles, and the operators aren't typically concerned with engine life. They're frequently worked hard from the minute they are started in the morning, and still rarely suffer engine failure before the chassis is done.

So if damage is done by moderate RPMs at lower speed, wouldn't company vehicles see frequent engine failures? Heck, wouldn't most vehicles driven by those that aren't "car people" see failure long before the service life was up? I just haven't seen it.

 

All valid points!

I guess at the end of the day, I feel like the high idle is a win-win-win scenario FOR MY SITUATION... I get some heat into the motor before I load it up (who knows if that does or doesn't help?), I get some heat in the cab sooner and I minimize wet stacking associated with regular idle. There are trade-offs such as still potentially a bit of wet stacking with high idle (again, who knows for sure?), EGR crudding, DPF fouling, fuel economy/cost and slightly increased environmental footprint but I feel that they are worth it to have a vehicle that is liveable in winter. Of course, I'll be going to syn oil at next change and will always monitor oil level and do changes when recommended by the smart monitor. Perhaps a bit of my logic is admittedly wishful thinking but I don't feel like high idling for 10-15 mins on really cold days is going to be a 50% decrease in engine life. If it is in the 5-10% range even I could live with that to have a comfortable daily driver diesel with a motor that will still likely well outlive the chasis. And there is still (in my mind anyway) a slight potential benefit from driving (ie, loading/revving the motor) the truck at closer to operating temp since my daily commute is quite short and I normally don't get up to full operating temp in that time. And I certainly don't feel that the potential trade-offs are worth the cost of buying and maintaining another vehicle for non-towing related daily driving duties.

My logic is infallible - muahahaha!!!!!!!

 

Our trucks don't always lock the torque converter when ice cold either.

On a side note, if you've ever manually shifted into sixth (of course well into operating temp) without getting the torque converter to lock (it's possible) and punch it, it's some serious fun.
Not that it's a rocket in sixth gear but it simply amazes me how much power it has in sixth prior to the TC lockup at 2,000 RPMs and 21 PSI boost!

 

You should see 37 psi of boost if you like 21 psi....

 

I like my warranty so 21 psi works just fine! LOL.

...but I can imagine.

 

It always is...seems that convincing someone of a way that's not their own is nearly impossible! No matter though, I don't think any potential harm from a few minutes a day of idling would be overly significant. Short commutes pose a different problem, and hopefully you get your truck up to operating temperature at least once or twice a week to burn off any crud that accumulates in the oil.

Thanks for the debate, it's always enjoyable when nobody gets offended.

 

Couldn't agree more! And thanks for the advice, I always get out for a good blast or two, especially on the weekends. I was mostly concerned about the DPF but this gives me yet another excuse to go showing off my truck!

 

Trying to stay neutral here...

at my place of business, we have all dodge diesels, all 6.7's. We were on a job were the worker had to stay on standby at the jobsite 12 hours a day 7 days a week, that was about 2 1/2 months ago, and he's still there.

He let his truck idle all day because he had to sit in it. after about 2 months, there was a warning on the dash that said regen, and it wouldn't go over 10 mph. Along with this, over the weekends we found out that he was putting off road diesel in it since he didn't have a company card, and there was a fuel cell on site.

I have heard rumors about each, but what killed the truck? I know from having a 6.4 that the pain in the butt dpf can plug up from things like this (which is why I deleted mine) and I've heard that running off road will hurt newer motors.

I will say this: 90% of our trucks idle around 4-5 hours a day and we have about 40 of them. Nobody has a dime in them, and they like a toasty truck in the winter, and a cool truck in the summer. The trucks normally get moved around the jobsite a few times a day, but at speeds around 5mph for only a couple hundred feet at a time. the trucks are starting to see 100,000 miles.

People have been idling diesels and gas motors for years. The one situation was excessive I know, but in my industry, the companies own the truck and the people who drive them could give a rats ***. most other companies in my industry have fords. These are people that are guaranteed to beat on their truck more than most, and they stay around awhile.

Is it GOOD to idle a truck for more than 15 minutes? probably not.

Does it MATTER that you idle more than 15 minutes? I doubt it.

Look into what companies do to their trucks, then look at what you do to yours. they are tougher than you think.

 

Tom, my gassers comment was referring to the difference that a gasser can reach normal temps just idling without any load.

 

Very well stated, ProgDrummer, reps sent!

Makes sense, thanks for the clarification!

 

This thread turned out to be a very good discussion. Props to everyone who is contributing!