Re: [A/S] Answers to Two questions

["duke748bp" <pbarlow@xxxxxxxxxxxxxxx>]

At work right now we are trying to get the big rig truck drivers
 to stop leaving there diesel engines running while the go for 
breakfast and while the truck is loaded, this is for enviromental
reasons. These are the facts we have so far found on idling diesel
engines.
        Brian in Canada
	According to Caterpillar engineers, for instance, fuel costs 
can be cut by up to 13% just by shutting down the engine instead of 
letting it idle. That can mean significant fuel savings. 
Several studies have shown that during idling, additional engine wear 
occurs. Cummins engineers say that whenever coolant temperatures are 
below 160°F (as in an idling engine), diesel fuel does not burn
well 
or completely. This causes carbon buildup and fuel slobber from the 
exhaust. 
During long periods of idling (more than 10 or 15 minutes), carbon 
can clog injector spray holes and piston rings and cause the valves 
to stick. If the engine coolant temperature becomes too low, raw fuel 
will wash the lubricating oil off the cylinder walls and dilute the 
crankcase oil. As a result, not all moving parts of the engine will 
receive enough lubrication. 
The bottom line is increased oil consumption, low power and greater 
engine wear. Caterpillar also says that lower operating temperatures 
can cause water vapor to form and condense in the crankcase. Here it 
combines with sulfur oxides to create sulfuric acid, which attacks 
bearings, rings and cylinders, as well as other engine components. 
Myths
A common belief was that idling was better for a diesel engine than 
shutting it down and restarting it. Although this may have been true 
with older diesel engines, it's not true with today's fuel-efficient 
electronic engines. 
Modern engines need to idle only about two minutes to cool down, even 
after running long and hard. The improved fuel metering systems and 
higher compression ratios in today's engines also mean fewer cold 
temperature start-up problems than in the past. At 30°F and above,
a 
properly maintained, electronically controlled engine should have no 
problem starting. 
Is there a trade-off between saving on fuel and wearing out the 
starter? According to Caterpillar, over the life of an engine, the 
fuel savings from shutting down an engine will far outweigh the cost 
of rebuilding or replacing a starter. 

According to the information from the website of the city of Toronto  
Canada, an idling diesel engine
will burn about 2.5 litres per hour and an idling gasoline engine 
about 3.5 litres per hour.
 They estimate that 10 seconds of idling uses more fuel than 
restarting  the engine