Idle Time: Notes

Idle time start times vary among manufacturers. Idle time counts may start when an engine has been below a given RPM for 15 seconds, three minutes, five minutes, etc. The two major variables in measuring idle time are:

• the RPM below which the engine is considered to be at idle
• the amount of time that goes by before the ECM starts counting the time at idle

For example, one engine may count idle time when the engine is below 800 RPM for 15 seconds while another counts it as below 1,000 RPM for three minutes. The difference between the two engines may not be large in sleeper cab linehaul operation, but it may be significant in day cab city operation. In some engines, these two parameters are programmable. Thus, to get comparable idle time, fleet managers must have the parameters that affect idle time calculations programmed similarly.