Thank you! That explication makes perfect sense. Exactly what I was looking for.My experience is mostly with agriculture and construction diesels but still applies, I think. Older diesels were much more friendly to longer idling, however newer diesels with the emissions you need to be careful with extended idles. To help keep the emissions systems clean its best to keep the engine hot/working, when an engine is not getting up to temp is when build up occurs (like short trips, long idle, etc). With my newer equipment, Tier 4, we warm the equipment up for about 5 minutes prior to work and a 5 minute cool down before shutdown, with a shut down if the break is longer than 15 minutes. In the winter we move warm up closer to 10 minutes, cool down is still 5 minutes, but if it is colder than normal we will allow the equipment to idle up to 30 minutes if we expect to resume work within that window. Every mechanic I have talked with say the same thing, the new diesel engines need to be working and to limit unneeded idling as much as possible. Short idles or longer if it is particularly cold should be fine but long idles can actually be harmful to the system.
Also if you’ve been pulling a heavy trailer at highway speeds and you just need to stop for Fuel, it is best to let the truck idle to let the Turbo cool down. The Turbo is cooled by the flow of oil and if the truck is idling then oil is flowing into the Turbo thus helping it to cool down. We use a similar approach for large industrial Diesel Generators, after a we run one with a load we have them set up with a 5 minute cool down timer specifically to let the Turbos cool down. Also there’s not much harm in letting the engine idle if you are just stopping for fuel as the compression ratio is so high at idle that it burns very little fuel. And there is no danger of fumes igniting like there is with gasoline. But as another posted, I would avoid long extended periods of idling due to the newer emissions equipment.When refueling with diesel, do you shut your truck off?