Is idling hard on motor oil? If so - then why?

Joined
Feb 24, 2009
Messages
75
Location
California
These days I find myself at lots of red lights and drive throughs - and I always wonder if idling is good for the engine oil or bad.
 
Joined
Aug 21, 2008
Messages
25,050
Location
ON, Canada eh?
Idling isn't good because the engine is running hot with little airflow other than the radiator fan kicking on occasionally to stop the engine from overheating. it is also not running at peak efficiency as it has to run richer to keep it idling which can cause oil dilution. Also the oil isn't flowing as fast and may not cool and lubricate the parts as well as when running above 1K RPM. With modern fuel injection technology its much less of an issue compared to earlier fuel injection and carbeuration, but it does cause slightly more deposits in most engines. (some more than others) If it can be avoided, this is best, but sometimes it can't...
 
Joined
Jan 10, 2008
Messages
4,998
Location
Milwaukee, WI
Hot idle is the time when you will have the lowest oil pressure. That isn't good. With little airflow, low oil flow and low coolant flow there is little cooling going on.
 
Joined
Jul 20, 2008
Messages
931
Location
Michigan
I used to be in sales and sit in the company car idling for hours every week typing on my computer ...even during 90 degree days in the summer with the air cond. on constantly. Never a problem even with 5,000 mile oil changes. It used to be the issue with gas getting into the oil in carb engines...poor oil cooling etc...
 
Last edited:
Joined
Sep 28, 2002
Messages
39,802
Location
Pottstown, PA
YMMV. If everything is up to snuff, it just gives your odometer less meaning in terms of when to change the oil. You're getting ZERO mpg while idling.
 
Joined
Jan 20, 2003
Messages
18,449
Location
East of IGO
It is really not worrying about in the whole picture of things you car will fet run into before any noticeable "bad" stuff will happen.
 
Joined
Jul 3, 2005
Messages
36,200
Location
NY
Just look at what the Police do to their cars. They hold up pretty well considering.
 
Joined
Aug 21, 2008
Messages
25,050
Location
ON, Canada eh?
 Originally Posted By: alphasparky353
So if idling with ac on, with fan going would that help keep temps down?
No because the engine is under excess load. I have monitored my coolant temperature with my Scan gauge both with the A/C on and off and it runs about 10 degrees hotter with the A/C running in traffic. ;\)
 

Bill in Utah

Staff member
Joined
Nov 11, 2002
Messages
12,849
Location
UT
We sit in our trucks for hours on end filling out reports and powering all the accessories. We get many miles out of our engines with no concerns. I will say that since Fuel injection the engines seem to be easier on oil when idling. In our Toyota's the water temp stays within 5 degrees no matter what I'm doing. 4x4, sitting, responding or driving around. They seem to have a pretty good control on the temps. When we had Fords the temps were all over the place. But the last model year we had them was 1999-2001. Never had a Dodge even though we had them. Now with all that said, the most I idle my own vehicles is a max of a couple of minutes. I just don't want the by products getting in my oil. Take care, Bill
 
Joined
Oct 11, 2002
Messages
22,187
Location
Colorado Springs
 Originally Posted By: StevieC
 Originally Posted By: alphasparky353
So if idling with ac on, with fan going would that help keep temps down?
No because the engine is under excess load. I have monitored my coolant temperature with my Scan gauge both with the A/C on and off and it runs about 10 degrees hotter with the A/C running in traffic. ;\)
Depends on the fan settings. Most GMs will idle darn near at 230, since the fans turn on slow speed at 220ish, high speed 230ish. Click the A/C on and the fans instantly go on high and stay on and the coolant temp will drop to around 200.
 
Joined
Aug 21, 2008
Messages
25,050
Location
ON, Canada eh?
My cooling fan has 3 speeds and is the only fan I have. It is on slow when sitting in traffic up to medium, and then goes to fast when the A/C compressor kicks in/out. My engine in summer heat usually sits around 195oF WT on the scan gauge and with the A/C running it's 205-212 oF
 
Joined
Jan 22, 2005
Messages
176
Location
Florida
I have an 05 F-150 4x4 V8 as a company vehicle. It has 140k on the clock and runs perfectly. It has thousands of hours of idle hours on it. There are days once I arrive to the job site, it will idle for 10+ hours, then a long drive home. It has done this since the day it was given to me with 5 miles on the odometer. Oil changes are every 5k, and haven't had the first engine-related failure or oil leak. Everything else has fell apart, except the motor... =)
 
Joined
Jul 4, 2003
Messages
3,118
Location
San Antonio, TX
 Originally Posted By: demarpaint
Just look at what the Police do to their cars. They hold up pretty well considering.
How many miles/hours oci does Ford recommend for Police Interceptors?
 

OVERKILL

$100 Site Donor 2021
Joined
Apr 28, 2008
Messages
47,202
Location
Ontario, Canada
 Originally Posted By: Chris142
The old pushrod V8's (and v6's too I guess) would eat cams if idled too much. The cams were lubed from oil thrown off the rods and at an idle not much oil got thrown.
What? There were many roller pushrod V8's, the SBF went roller in the Mustang in 1985..... Oil is pressure-fed to the lifters, which regulate oil flow to the top-end. Oil coming down the lifter bores lubricates the camshaft lobes, the camshaft bearings are pressure-fed.
 
Joined
Dec 21, 2003
Messages
12,385
Location
Northern CA
 Originally Posted By: ekpolk
Idling? What's idling?
Posting on a forum is the best definition I can come up with right now.
 
Top