OK, I have a friend (seriously!) who posited this:
Her father had told her (30 years ago) that it’s a bad idea to start up a car and just let it idle because [something about the valves might get messed up because of oil not circulating properly].
Any problems related to lubrication about just letting it idle (say, 30 minutes or less). I know that if your cooling system isn’t working properly that it can run hot, but I’m asking just about the oil system.
If your car is mechanically sound, 30 minutes of idle won’t deprive it of needed lubrication.
30 years ago there was sometimes a problem with fuel contamination of the oil when the car was idled extensively, but I believe that went away with the advent of electronic fuel injection.
I though that 30 years ago the recommendation was to idle your car when cold prior to driving. But today, it’s not recommended to do so. I don’t know if “not recommended” means the same as “recommend that you don’t,” though.
With modern cars, the vehicle is ready to go about as soon as you could get it in gear. That actually goes back to the EFI. The computer is pretty good at choosing the right ‘choke’ setting, and can run cleaner 4 seconds after first ignition than my old '77 Ford with the 4-barrel carb did a minute after first ignition.
By idling a newer car, all you’re doing is burning gas, polluting and putting wear and tear on the engine [1].
Newer cars are all running 5W20 or 5W30, while we saw 10W30 [2] and 10W40 in wide usage during the '70s.
[1] Ford Motors suggests that idling a Crown Victoria for 1 hour puts as much wear and tear on the engine and oil as driving 33 miles.
[2] Vintage 10W30 oils had much worse cold flow performance than you might see today.
Ah! It was for fuel and air (choke) reasons, not oil circulation reasons! That makes a lot of sense now. However, in the case of the Crown Vic, what accounts for the extreme engine wear? Let’s assume 33 miles is 1/2 hour, versus the hour idling. I could only think of inefficient cooling or oil circulation at idle being the root cause. What engine do they have? The 4.6 Modular, or something more archaic? Push rods and two valves? I’ll have to go look that up.
All post-91 Crown Vics will have the 4.6 modular in one form or another. I believe the CV proper has been 16 valve in all those years. Can’t recall about the Marauder…
The pre-92 LTD Crown Victoria isn’t properly referred to as a Crown Vic in any case.
As far as 33 miles worth of wear and tear on the engine goes, remember that fuel IS being burned and the pistons are in fact still travelling at idle. Particularly if you’re running the AC and some accessories, you’re putting some modest load on the powerplant.
I don’t know if I would use the word extreme in this case. Based on what I have seen on the average on board trip computer, very few if any cars average over 33 miles per hours. I don’t care if you drive 75 on the freeway, that red light at the end of the ramp brings the average way down. So does stop and go traffic, so does, rush hour, so do drive thrus. You get the idea.
I used to check the average speed on my customer’s cars when the car was in for service. If I saw over 23 MPH I was impressed. Most cars were between 15-18 MPH average.
So 33 miles is about the same as two hours of driving, or one hour of idling. While that is increased wear, is that really extreme?
Agreed. I drive 1/2 mile at 25-30 from my house to the on ramp, 30 miles on the freeway at 75-85, and 1/2 mile past the offramp to the office at 35-50. There’s only 1 traffic signal between the house & the onramp, and only 2 between the offramp & the office. Repeat 2x / day, 5 days /week.
I reset my trip computer at each fuel up (between the office & fwy on the way home) & it always comes in around 45 mph if I just include the commutes, or 35 if that tankful includes the weekend’s grocery shopping, etc.
While, that would mean that idling puts less wear and tear on an engine than driving it. Because in an hour, I could certainly drive more than 33 miles!
I once left my car in idle to charge a weak battery, and forgot about it overnight. It idled for at least 8 hours, and when I discovered it, it seemed no worse for wear. Still runs great as a matter of fact.
We need an hour gauge, like those found on boats, plus an ‘average RPM’ gauge…or better yet, a "total engine revolutions’’ gauge. Even so, you could narrow it down even further, because a long stroke engine is going to see more total parts movement (asa distance inside the engine) at a given RPM than a short stroke or ‘oversquare’ engine.
If you idled a 30-year old car for an extended period of time, it wouldn’t be surprising if you slightly fouled the plugs. It could leave to a temporary case of bad running, but sufficient RPMs should clean the plugs. I’m sure people came up with all sorts of conclusions over the years about what idling does to an engine.
FWIW, I average 27.8 MPH.
Could yes, but in reality probably don’t.
One reason not to idle your car is that it’s illegal in many places, typically anything over 3 or 5 minutes is a violation, with some exceptions for cold weather. (These are pollution control measures, but often incorporated into the regular traffic code)
http://atri-online.org/research/idling/2007_atri_idlingcompendium_secure.pdf
Looks like South Carolina might not have any regs at this time. Virginia though, apparently does.
I just checked the car I am driving. 16 mph average. So one hour of idling would be right on 2 hours of driving.
My friends I used to ride motorcycles with all had Japanese bikes. Before riding they would all start their bikes and let them idle for some time.
I had a BMW sport bike with a boxer engine that the manual explicitly stated NOT to let idle. So when they were ready to go I just started mine up and went.
I’m not comfortable with this assertion. At idle, the engine is turning something like 800 rpms.
When driving the 18 miles in the hour you would go on average, the average RPMS are probably way higher. I’ll bet the RPM average for 18 miles is something like 2200 RPMs, and I’m being conservative.
An hour of idling = 48,000 RPMs
An hour of driving = 132,000 RPMs
Check engine temp during idling.
If you’re idling at non-optimal temperature, wear numbers will be higher.
I wonder if your friend is either misremembering or misinterpreting a conversation about the “fact” that most engine wear is caused at start-up (no oil and all that). The “idle” part of the conversation may not have been important to her father, just the “start-up” part of the statement.
The ownser’s manual of my (new) car recommends that I let it warm up for 30 seconds before I drive away. I don’t usually bother, though.
Well, dudes have answered about it being bad for the car. But it is bad for your pocket, bad for the environment, gives a much greater chance of getting your car stolen, and as Quercus sez, can be illgela.
So, it’s damn stupid.