To Engine Idle or Not

[Gary Winzenburger]

My wife and I are new to RV'ing. We have a 1997 Marquis with C-12 Cat motor. This may be a silly question, but is there a major reason why diesel motors are allowed to idle for long periods of time like at interstate rest areas? You can always hear them running. It's not just big rig trucks, but RV's and busses too. Everything I've read/heard so far says I shouldn't idle the motor for more than 10-15 minutes, so what's the general opinion?

[Richard And Babs Ames]

Excessive Idile to me is over 5 minites. Any longer wastes fuel and causes oil contamination.

[Edward Buker]

When you come into a rest area and have run hard there is a reason to allow the engine to idle. It allows the turbo time to cool down some and the engine to reach some equilibrium temperature wise. 5 minutes is probably enough except for long stressful climbs. Idling a cold engine for long periods is probably not a good idea for gathering deposits on the rings. Start up, idle a few minutes or so to air things up, then start out keeping the output moderate if possible until the engine has reached normal operating temperature. You should accumulate less deposits the quicker you get a running diesel engine up to temperature so limit the idle time to what is needed.

Many of the trucks and buses are idling to keep the interior heated or air conditioned for the drivers and passengers. Some are told not to shut down for reliability issues when it comes to having to restart a diesel. That I can understand in cold weather but it sometimes seems to continue when not needed.

There is no good reason to idle more than 5 minutes that I know of just as Richard indicated.

Later Ed

[Tom and Pam Brown]

if you must leave on for heat of cooling or just because you want to, always idle the engine up a couple hundred RPMs with the cruise.  It saves fuel and keeps better oil pressure.

[Gary Winzenburger]

Thanks for the remarks - it all makes sense. As long as I can run the generator to heat or cool, I'll plan on shutting down the "yellow monster" during rest periods along our travels.

[William Brosam]

if its at night its to heat /cool power the living quarters or refridgerator unit.

if you pull into a rest stop after driving in high ehat or a mountain. and kill the motor what happens is you trap the oil, and water in the motor in the hottest locations and dont allow it to flow and keep all parts within the workign temperature, instead it has to cool by soaking and drawing the heat though the passageways which doesn't work as well.

a few minutues with the fan blowing, water pump running and oil pump chugging away usually has things cooled down enough.

if its extremely cold most never shut the diesels off as they may not start, but i doubt you will be RVing in -20*F or colder temps

[Joel Weiss]

a few minutues with the fan blowing, water pump running and oil pump chugging away usually has things cooled down enough.

One CAT document I read said that the necessary cool-down was on the order of ~3 minutes in order to cool the turbo sufficiently.  A comment was made that usually by the time you turn off the interstate to get into a truck stop you've probably been going slowly enough for long enough to be able to shut it down without further waiting.  The only time this isn't necessarily the case is when we pull directly off an interstate into a rest stop.  In those cases I usually let it idle for a few minutes.

[Gary Winzenburger]

I usually perform the same thing with gas motors, ie lawn mowers, chain saws, etc. in allowing them to idle a little before shutting them off. Thanks for all your advise and opinions!