CYLINDER GP 1630324 - Caterpillar

Caterpillar Truck EnginesFuel, driver, truck payment, insurance and general maintenance are all known "costs of operating a truck". These are the expenses the most efficient fleets and owner/operators try to minimize and keep under their control. Another "cost" that is often not addressed or given little emphasis is low idling operating expense.
"Low idle operating expense" can be divided into several categories. This article reviews the three primary categories:* Direct Cost (More obvious-Fuel Consumed)* Indirect Cost (Less obvious-Engine Wear)* The affect of idling on tank mileage
Direct Cost
Fuel consumed at idle in Caterpillar Truck Engines (3306, 3176 and 3406) varies from .35 gph to .42 gph in lab conditions. In-the-truck idle fuel consumption has been documented from .55 to .60 gph at 700 to 750 rpm. If the "low" idle rpm is raised to 1000, the in-the-truck fuel consumption will increase 50% (from .60 to .90 gph). Accessories will also add to the fuel consumption. See the following chart. Even though the actual fuel consumption is low, the cost is real.
It is difficult and/or expensive to accurately measure exactly how much a specific mechanically governed truck idles but with the electronics systems available today, truck owners can tell exactly the idle time on each truck. Currently, typical coast-to-coast operations with 2-man driving teams,have indicated that during the time the engine is running, 10 to 30 percent is idle time. For single drivers, 25 to 50 percent is idle time.
For example, if a truck accumulates 100,000 miles per year and idles 8 hours per day, 5 days per week, 50 weeks per year and consumes 1.10 gph, this truck's engine will consume 2,200 gallons of fuel per year. At $1.20 per gallon, thats an annual cost of $2,640. The direct fuel consumed from operating 100,000 miles per year at 6.5 mpg is 15,384 gallons. At $1.20 per gallon, the annual fuel cost is $18,462. If you add in the $2640 cost of idling, fuel consumption cost increases almost 15 percent per year. In this example, the fuel consumption cost increase to $21,102 per year. In many fleet records, this 15 percent fuel consumption increase, will not be subtracted from the "over-the-road" fuel consumption calculations. In this example, if the truck normally gets 7 mpg "over-the-road", the actual fuel consumption could easily be lowered 0.8 mile per gallon. (see Tank Mileage Fuel Consumption)
Indirect Costs
Although studies have been done to determine how much wear results when a truck idles, the bottom line is hard to quantify. Caterpillar studies indicate low engine operating temperatures at idle will allow water vapor to form and condense in the crankcase. The water in the crankcase will combine chemically with sulfur oxides (a by-product of combustion). This combination will result in sulfuric acid. The acid can damage bearings, cylinders, piston rings and valve stems, just to name a few. This damage will shorten engine life.
The cooling system on a typical diesel engine is designed to operate at 175 to 190°F. Excessive cooling, which can result from idling, can