While I love my little oil-burner, I don't appreciate my sleep-in or morning TV/radio being interrupted by a clattering diesel nearby or breathing diesel fumes over my breakfast. Fellow travellers who have not yet "seen the light" and still drive petrol vehicles are probably even more annoyed.
So I'd ask my fellow travellers: Please don't idle your diesel for long periods in the morning, especially in caravan parks. It's not good for your fellow travellers and it's not the best for your engine either.
Even modern diesels are still noticeably noisier at idle than petrol engines and it is annoying to most people to have their morning interrupted by the clatter of an inconsiderate neighbour's diesel idling for many minutes (or even tens of minutes) in the morning.
Proponents of long idling will now arc-up and say they need to idle their engines to warm them up before moving off.
Well, from what I have learned about diesels, this is not the best way to do it.
Of course it is desirable to bring any engine to close to normal operating temperature before subjecting it to heavy loads such as accelerating a heavy caravan or trailer up to highway speed. But long idling is not the optimum way to do this and even a very long period of idling is unlikely to achieve it with a diesel engine.
At idle, both petrol and diesel engines are burning very small amounts of fuel and it takes a considerable time for appreciable heat to be generated in
the block and coolant jackets. And as the cylinder and combustion chamber surface temperatures are
well below normal, a significant portion of the fuel condenses or collects on the cylinder walls and the fuel system has to add extra fuel to ensure enough fuel is available to support combustion. The fuel on the cylinder walls dilutes the lubricating oil film and some of it passes the piston rings and permanently dilutes the lubricating oil.
The problem is worse with diesel engines as, unlike petrol engines which run air/fuel ratios of around 15:1 at all times, a diesel engine at idle may have an air/fuel ratio of greater than 100:1. So every induction stroke a large unthrottled air charge enters the cylinders and removes much of the residual heat from the last power stroke. Then most of that slightly heated air is expelled in the exhaust stroke. So it will take a very long time for the engine to "warm-up", it at all. Under cold ambient conditions it may never approach normal operating temperature at idle.
So, extended idling of a diesel results in a slow, ineffective warm-up at best and certainly contributes to excessive oil dilution. Please correct me if I'm wrong, but I have yet to see a vehicle owners manual that recommends long idling after start-up. In fact, the recommendations for Cummins heavy-duty diesel engines used in many large trucks, etc. specifically warn against idling for longer than 5 minutes after start-up, especially during the "run-in" period.
Please note, I am not recommending immediate drive-off and heavy loading of a stone-cold engine. My research suggests a reasonable method of warm-up would be:
Turn-on ignition until the glow-plug/start assist system indicates it is ready to start.
Start the engine and run at idle for long enough to ensure full oil pressure and flow is established (typically 30 seconds would be more than sufficient).
Drive-off gently and avoid loading the engine heavily until the coolant temperature gauge is
well on it's way to it's normal position on the dial.
Idling the engine for 10 minutes or more while completing the coupling-up of your caravan/trailer is unnecessary, inconsiderate and counter-productive.
If you have remained hooked-up overnight and perhaps have no choice but to accelerate rapidly onto a busy highway immediately upon leaving the park, might I suggest you leave your site as quietly as possible and drive to the park exit (
well away from other guests if possible) where you might give the engine a minute or two to warm-up at a fast idle before 'hitting the highway'. But I'd suggest this would be a rare situation.
I'm sure there will be some who disagree strenuously with me on this issue but I'd ask for contrary responses to be based on fact (such as quotes from owners' manuals or technical sources rather than hearsay or urban myth. [Hearsay may be OK for US military commissions, but it's definitely not acceptable on the ExplorOZ
Forum!!]
Ian