Diesel Engine vs Gas Engine During Long Periods of Idling...

**StockEngine** · March 29th, 2019 07:31 PM

Originally Posted by oj88

That practice is always detrimental to the engine's health. Long idling creates more carbon build-up, contributes to fuel dilution in oil, increased cylinder wall wear, which then results in more blow-by.

It's especially bad for modern Diesels equipped with DPFs.

As the effects are not immediate, many people see engine idling as harmless. But there's a reason why long idling and/or stop and go traffic, among other things, are considered severe or extreme conditions on almost any vehicle owners manual.

carbon buildup where? intake ports?

oil dilution.. only when the owner doesnt change at proper intervals.

cylinder wall damage? related to above but again.. not an issue if owner does proper oci for our hardly moving traffic

**12vdc** · March 29th, 2019 08:36 PM

^EGR opens during those idling moments, hence the more exhaust gas passing the intake and the more it makes the oil acidic.

**oj88** · March 29th, 2019 11:35 PM

Originally Posted by StockEngine

carbon buildup where? intake ports?

oil dilution.. only when the owner doesnt change at proper intervals.

cylinder wall damage? related to above but again.. not an issue if owner does proper oci for our hardly moving traffic

Carbon buildup in the combustion chamber, pistons, valves, and downstream of it to the cat or DPF.

Lookup cylinder wall glazing. Glazing means that the factory crosshatch has been polished off due to the unburned/excess fuel from long idling, washing off the coat of oil off the cylinder wall. Long idling also does not produce enough combustion pressure for the piston rings to seal properly, thus allowing unburned fuel to seep through. The crosshatch is there for oil to stick to, working in conjunction with the piston rings to seal as much of the combustion as possible. With the crosshatch polished off and as it becomes shiny and smooth, oil doesn't cling to it as much and no amount of OCI regimen would fix that. The block is essentially ruined.

As a result of cylinder glazing, more blow-by gasses can get through, accelerating fuel bi-products dilution of the oil, as well as reducing the compression ratio and the overall engine performance.

Increased blow-by will also inject more oil back into the intake via the PCV system. So, going back to your first question, that will definitely be a source of carbon buildup on the intake valves, particularly on DI engines.

**SidCoronel** · March 30th, 2019 09:35 AM

Originally Posted by attyallanlatras

I usually see owners/drivers of vans (Hi-Ace, Urvan, Starex, and the like) running their engines with the aircon on for several minutes like for more than 30mins to an hour at the parking area. I know these are diesel engines. But is this okay? What are its adverse effects, if any? .

1) Your ride will be "older" than its mile-age... 800rpm x 30mins = 24,000 revolutions older = engine wear. Same strain on compressor and other rotors

2) Pollution, which a lot of people don't care about as long as they are comfortable in a cold cabin.

**SidCoronel** · March 30th, 2019 09:39 AM

Originally Posted by attyallanlatras

I usually see owners/drivers of vans (Hi-Ace, Urvan, Starex, and the like) running their engines with the aircon on for several minutes like for more than 30mins to an hour at the parking area. I know these are diesel engines. But is this okay? What are its adverse effects, if any? Fuel consumption? Is this practice ok because they are vans? what about SUVs doing this, what would be their difference?

How about those cars on gas engines also doing this practice of running their engines with the aircon on for several minutes?

Pls enlighten me on this. I am not doing this to my ride (Fortuner Diesel AT 2016), but still I am curious.

Originally Posted by oj88

Carbon buildup in the combustion chamber, pistons, valves, and downstream of it to the cat or DPF.

Lookup cylinder wall glazing. Glazing means that the factory crosshatch has been polished off due to the unburned/excess fuel from long idling, washing off the coat of oil off the cylinder wall. Long idling also does not produce enough combustion pressure for the piston rings to seal properly, thus allowing unburned fuel to seep through. The crosshatch is there for oil to stick to, working in conjunction with the piston rings to seal as much of the combustion as possible. With the crosshatch polished off and as it becomes shiny and smooth, oil doesn't cling to it as much and no amount of OCI regimen would fix that. The block is essentially ruined.

As a result of cylinder glazing, more blow-by gasses can get through, accelerating fuel bi-products dilution of the oil, as well as reducing the compression ratio and the overall engine performance.

Increased blow-by will also inject more oil back into the intake via the PCV system. So, going back to your first question, that will definitely be a source of carbon buildup on the intake valves, particularly on DI engines.

Interesting... Do you think the same "glazing" applies to power generators, especially the portable ones?

**SidCoronel** · March 30th, 2019 09:44 AM

Originally Posted by StockEngine

carbon buildup where? intake ports?

oil dilution.. only when the owner doesnt change at proper intervals.

cylinder wall damage? related to above but again.. not an issue if owner does proper oci for our hardly moving traffic

If the recommended oci of an oil is 10k kms, considering "our hardly moving traffic..." When do you recommend to do the oil change?

**StockEngine** · March 30th, 2019 10:05 AM

Originally Posted by SidCoronel

If the recommended oci of an oil is 10k kms, considering "our hardly moving traffic..." When do you recommend to do the oil change?

every 6mo is good practice. at that time the airfilter and ac filter is probably so dirty already anyways.

**oj88** · March 30th, 2019 10:36 AM

Originally Posted by SidCoronel

Interesting... Do you think the same "glazing" applies to power generators, especially the portable ones?

Short answer is a likely, yes.

Long answer. In the context of emergency power generators, engine wear is kind of a given and is usually sacrificed for instantaneous and unplanned emergency operation. Many of these typically large generators are automated and will start itself upon sensing a power failure and immediately rev-up to a usual 3000 RPM and immediately supply power to its load (used mostly in hotels, malls, hospitals and large commercial establishments), without so much as a 10-second warm-up.

But one factor that affects the cylinders is the loading. Under-loading a genset is as bad as running it at idle for long periods of time. This link suggests that Diesel engines must be loaded at around 60-75% of its total capacity to provide adequate seal on the piston rings and prevent or at least reduce the possibility of glazing.

In other words, don't put a 10kVA genset when a 3 or 5kVA is all you need... UNLESS there's absolute value in having a higher kVA headroom over the life of the genset.

**StockEngine** · March 30th, 2019 10:37 AM

Originally Posted by oj88

Carbon buildup in the combustion chamber, pistons, valves, and downstream of it to the cat or DPF.

Lookup cylinder wall glazing. Glazing means that the factory crosshatch has been polished off due to the unburned/excess fuel from long idling, washing off the coat of oil off the cylinder wall. Long idling also does not produce enough combustion pressure for the piston rings to seal properly, thus allowing unburned fuel to seep through. The crosshatch is there for oil to stick to, working in conjunction with the piston rings to seal as much of the combustion as possible. With the crosshatch polished off and as it becomes shiny and smooth, oil doesn't cling to it as much and no amount of OCI regimen would fix that. The block is essentially ruined.

As a result of cylinder glazing, more blow-by gasses can get through, accelerating fuel bi-products dilution of the oil, as well as reducing the compression ratio and the overall engine performance.

Increased blow-by will also inject more oil back into the intake via the PCV system. So, going back to your first question, that will definitely be a source of carbon buildup on the intake valves, particularly on DI engines.

fuel washing off the oil... this doesnt happen on every car idling though. even it does..only way for ordinary folks is changing the oil 2x a year.

**oj88** · March 30th, 2019 11:01 AM

Originally Posted by StockEngine

fuel washing off the oil... this doesnt happen on every car idling though. even it does..only way for ordinary folks is changing the oil 2x a year.

It's not as significant when idling for a few minutes. But in the context of the OP's original post, idling for 30 minutes to a few hours everyday, therein, as they say, lies the rub.