Cruise control is caps lock for.. wait a minute..

October 31, 2009 5:09 PM

Is using cruise control all the time bad for my car in any way?

To prevent myself from speeding, I like to use cruise control almost all the time. I did this with my old car, a 2000 Pontiac Firebird, with no discernible ill effects. I just got my first NEW new car (a Nissan Cube SL with a 4 cylinder CVT transmission), and want to make sure I'm not doing anything that could damage it.

I do not try to use the cruise control in stop and go traffic, but other than that, I do. Whether the speed limit is 25, 35, 45, 55, 65... you get the drift. If I'm going a long-ish stretch at any particular speed, I just set the cruise control. Could this cause any problems for the car?

posted by srrh to travel & transportation (27 comments total)

No. Cruise control is just an electrical/mechanical circuit that is emulating what you'd be doing with your feet anyway. As long as you're paying attention to the road, you're fine.
posted by dacoit at 5:12 PM on October 31

Nope. If your car is a manual transmission, CC might cause it to lug up hills, but most modern cars don't have a problem with that any more. (Really.) If it's an auto, the car will downshift as it needs to.

Assuming you're not doing anything risky with it otherwise, it's perfectly safe.
posted by TheNewWazoo at 5:13 PM on October 31

It's not a very good driving habit to get into. Your feet are off the pedals which can increase braking response time. Depending on how efficient your cruise control is (not sure if the Cube has electronic control or the older vacuum setup--probably the former since it's new) you might also see a reduction in gas mileage since the throttle is constantly being adjusted. Otherwise, I doubt any real mechanical problems would arise. Perhaps the switchgear on your dashboard/steering column might wear out more quickly.
posted by Burhanistan at 5:15 PM on October 31 [3 favorites]

Contrary to Burhanistan I've heard that cruise control is actually BETTER for gas mileage, as the computer is more consistent on gas than your shaky foot is.

I drive the same way for over 10 years now and I've never had any car issues related to cruise control. Anecdotal for sure, but I think you're in the clear. I imagine if there was some issue like that, our mom's would be getting chain emails about it from their friends.
posted by toekneebullard at 5:27 PM on October 31 [2 favorites]

No problems. Rock out with the cruise control to your heart's delight. You will be rewarded with good gas mileage and low maintenance/repairs bills. Enjoy!
posted by torquemaniac at 5:29 PM on October 31

There are conditions when you SHOULD NOT be using your cruise control : rain or snow
posted by bluefrog at 5:50 PM on October 31 [1 favorite]

Of course there's no problem using it frequently. That's what it's for! Car manufacturers wouldn't put cruise control on cars if it would cause damage by using it.
posted by bengarland at 5:51 PM on October 31 [1 favorite]

Burhanistan is right, I think, both that it's probably not as safe and that, presumably, if you use the cruise control a lot it might wear out faster.
posted by box at 6:06 PM on October 31

Using cruise control at slow speeds is not advised for safety reasons. I've read in my owner's manuals on some cars I've owned where it says it won't engage at lower speeds (like below 32mph or km/h equiv) for that reason.
posted by birdherder at 6:17 PM on October 31

Another vote for better mileage, no damage. You're not going to 'burn the circuit out', and you've probably already noticed that CC is much less aggressive in shifting than the typical human driver.
posted by unmake at 6:23 PM on October 31

If Burhanistan is right, I'd like to see the study. I've always heard the opposite but I don't have a study to point to either. As for damage to the car: No, it's fine. The only problem I've ever heard of is the control circuit can fail and the throttle can go wide open (the car goes full throttle). This happened to my mother about 15-20 years ago so I don't think it's very likely anymore.
posted by chairface at 6:27 PM on October 31

The mileage thing probably comes into play in hilly areas where you might otherwise let your speed reduce while climbing. The cruise control will downshift and keep the set speed. On flat stretches, it would be more constant and probably use marginally less fuel.
posted by Burhanistan at 6:31 PM on October 31

No answers, just anecdotes. I rented a car recently and found the lowest it will cruise is 25mph (some little white thing, I think a Kia or the Versa). The highest it would cruise was 80.

I use cruise on streets I'm familiar with that "feel" fast but aren't, or when driving a new car to make sure I don't go fast when it doesn't "feel" fast to avoid ticketing (how I got my first speeding ticket ever - it didn't feel as though I were going fast at all.
posted by tilde at 6:46 PM on October 31

The Car Talk guys say you can't wear it out, it does get you better mileage, but they have some safety reasons why you shouldn't drive around town with it on.
posted by donnagirl at 7:23 PM on October 31

Burhanistan is right, I think, both that it's probably not as safe and that, presumably, if you use the cruise control a lot it might wear out faster.

No. (S)He isn't right. Sorry. I know we're supposed to be respectful of opinions and all, but it's just incorrect.

You aren't going to wear it out. It's an electronic circuit. Normal operation causes no wear whatsoever. You'd need to overvoltage it by, say, jamming jumper wires into the onboard computer or something similar.

In addition, many modern cars have a fly-by-wire throttle pedal--and the Nissan Cube is one of them. Your pedal is connected to a little potentiometer which reads how far down you've pressed the pedal, and then the computer opens the throttle body appropriately using a little servo. There is no physical linkage between the throttle body and the throttle pedal--it is all, and always, mediated by the computer. No part of the car cares, at all, whether the electronic signals are coming from the cruise control or from your pedal's position. They're 100% equivalent.

Furthermore, in my own testing, cruise control provides better fuel economy for me. When not using cruise control, my speed varies constantly over a 3-5mph range. This means that I'm engine braking (I drive stick) some of the time, and then must burn extra gas accelerating back up to the target speed. Cruise control keeps it inhumanly steady. My numbers came out to something like 1mpg better fuel economy using cruise control on highway drives. This was over about 600 miles for each test condition (I get bored on road trips and amuse myself with these sorts of tests).

Finally safety... now, at least, we have something to discuss.

I think it depends on how you treat cruise control and what the road conditions are. If you treat it like autopilot--like, hit cruise and then do your toenails--, then you're destined for a terrible road accident. If, however, you maintain the same level of awareness and attention as you do when not using it, I can't see how it's less safe.

Anecdotally, I use cruise control all the damn time when I'm on the highway. In the course of a 25 mile highway drive, I'll turn it on and off ten times as I deal with traffic situations. But it'll only be off for a couple minutes total. And I've never had anything even resembling an accident... and I've stopped before, and swerved to avoid, many a deer.

The only cogent argument I can see for its safety is that you may, psychologically, be more likely to close in on a slow car in front of you. That is, since "you aren't controlling the speed", that you might be more willing to simply let your car close in on the one in front of you. Again, if you're a competent driver and paying attention, you'll notice when this becomes a problem and correct it.

Your feet are off the pedals which can increase braking response time.

So, let's say you're rolling down the highway at 65mph with your foot on the throttle. A deer jumps out in front of you. You have to release your foot from the throttle, move it over, and then stomp on the brakes.

If you're running on cruise control, all you have to do is move your foot to the brakes and stomp.

I'm having trouble seeing how there's any difference. If anything, you can get from the floor-mat to the brakes more swiftly than you can from the throttle to the brakes.

You're not using both feet to drive, are you?
posted by Netzapper at 7:49 PM on October 31 [7 favorites]

I didn't say it was going to wear it out faster, only possibly the switchgear.
posted by Burhanistan at 7:52 PM on October 31

I didn't say it was going to wear it out faster, only possibly the switchgear.

[I'm not sure what a switchgear is. I assume you mean transmission.]

Not on a stick shift, and not on a CVT (continuously variable transmission). Maybe on an automatic transmission... but most modern cruise controls stick with the highest gear usable for that speed specifically to avoid flipping back and forth between two gears. Even on an older car, you have to pick a transitional speed (at the top of one gear, and the bottom of the next) in order to get it to flip back and forth.
posted by Netzapper at 8:05 PM on October 31

Read my comment. The switch on the dashboard.
posted by Burhanistan at 8:09 PM on October 31

This will cause ZERO problems for your car.

Modern cruise control consists of zero extra parts or components. Most manufacturers have switched to a "drive-by-wire" system whereby the throttle has a control module and actuating motor that receives input from the Engine Control Module based mainly on accelerator pedal position. In a modern car, stepping on the gas does nothing physical other than input to the Engine Computer that you want more power output.
By selecting "Cruise" you're probably not engaging any physical mechanism at all. Rather, you're activating a program in the ECM that takes your current speed and varies the throttle plate and transmission gear selection in order to maintain your selected speed.
This is vastly more efficient and dynamic than previous vacuum diaphragm style cruise control which was a simple mechanism to lock the throttle in the selected position. Since this was a "dumb" system, it would often cause transmission "hunting" and poor performance going up and down hills, etc. These effects are especially reduced since you're using a CVT which isn't limited to a predetermined and finite number of gear ratios.

Enjoy your new Nissan!
posted by Jon-o at 8:27 PM on October 31

Once the car is worn in, there is no problem with using cruise control all the time and it will, as others have said, be better on the mileage.

One issue to be mindful of though is that running an engine/transmission at one single speed for long distances when it's brand new can cause uneven wear issues. The usual advice is to vary your speed occasionally for the first few thousand miles - not a problem if you live in a hilly place or on city streets with constant acceleration/deceleration, but might be an issue on freeways. Say you're in a 65-zone, set it to 63 for a few miles, then 67, then 69, then 65, or whatever. Little variations.

Once you've done 3000 miles or so, go nuts on the cruise control.
posted by polyglot at 8:58 PM on October 31

Much better for fuel economy, as long as you are on flat ground.

Where it's questionable is on hills. Cruise control will try to maintain constant speed which isn't what you're likely to do with your foot (unless you're a leadfoot, in which case pissing away fuel is your usual strategy).

The maintenance of constant speed is also what makes it dangerous on slick/windy roads. You'll notice that as you approach a corner, if you don't intervene it feels like you're accelerating. This is because you usually instinctively lift off the throttle and slow down. Cruise control just keeps at it (which causes me a little moment of panic if I wait too long to decelerate).

Also, cruise control doesn't know when to be gentle with the throttle. If you're rounding a slick corner, and it decides to accelerate, it will simply jam the throttle down and you risk spinning out.
posted by klanawa at 10:19 PM on October 31

Its not a very good idea to use it during any slippery conditions (rainy, snowy weather, etc.), or hilly mountainous areas. The hilly or mountainous areas can be hard on your transmission while its on cruise. Using it will increase your gas mileage on the flatter, straighter roads though. But there are a lot of variables, wind and traffic being just a couple. I recommend reading your owners manual.
posted by Taurid at 10:33 PM on October 31

One issue to be mindful of though is that running an engine/transmission at one single speed for long distances when it's brand new can cause uneven wear issues. The usual advice is to vary your speed occasionally for the first few thousand miles - not a problem if you live in a hilly place or on city streets with constant acceleration/deceleration, but might be an issue on freeways. Say you're in a 65-zone, set it to 63 for a few miles, then 67, then 69, then 65, or whatever. Little variations.

This. Don't do it for the break-in period. The gears in your transmission and final drive have been machined from the factory, and there's a little bit of initial wear that's going to take place during the break-in period. What you do not want to do is maintain a steady speed; instead, you want to accelerate a little, back off a little, every minute or two, so that the wear takes place evenly on both sides of the gear teeth (as one side is stressed during acceleration and the other when coasting.) Typically if you hold extended steady speeds during the break-in period, you might end up with a bit of gear whine over the life of the car, so we're not talking about anything tragic, but potentially annoying.
posted by davejay at 11:05 PM on October 31

Thank you for asking this question. I often forgetfully leave the button on when I am not using the cruise control, and I use it quite often on the highway. Last week my mom drove me to the eye doctor in my car and practically yelled "WHY is your cruise control on?!" I am going to show her this thread. She thinks you shouldn't use it unless you're on a long road trip.
posted by IndigoRain at 11:25 PM on October 31

I tend to use cruise control on the highway. If I go in the slow lane and set my speed to slightly (1-2 mph) slower than the car in front of me, then I hardly ever have to touch the brakes because there's always wide open space ahead of me.
posted by randomstriker at 1:32 AM on November 1

No mechanical damage subject to the various caveats above.

Probably it gives you "good" but not the very best possible mileage. If you are heavy on the pedal and constantly adjusting, then cc would provide relatively better mileage. If you are a gentle driver and generally keep very constant pressure on the pedal (letting the speed drift up and down with the gradient), then you can expect better mpg without cc. It is my understanding that the very best mileage is obtained by maintaining absolutely constant pedal pressure, even as the speed varies. On the other hand, the cc by design varies the pressure to maintain constant speed.

Elapsed time to move your foot to the brake would be the same except when not on the gas pedal you loose your positional reference; might take an extra part of a second to find the brake. Here's what I do to mitigate safety issues when on cc: (1) if road conditions/traffic start to get a little complicated, immediately turn it off, e.g. when navigating through a pack of slower cars; (2) if there is a momentary safety issue, such as someone passing me on a country road, I hover my foot over the brake to facilitate faster than normal braking action; (3) sometimes I will rest my foot over or lightly on the accelerator pedal so that I know precisely where it is (though that somewhat defeats (no pun intended) the purpose of cc).
posted by Kevin S at 8:03 AM on November 1

I have a 1997 Saturn, so maybe this doesn't apply to you, but with my cruise control, if I'm using it and I'm going up a hill, even very gradually, it can cause my engine to rev up into the 4-5000 rpm range, which I'm assuming is not good for it at all.

It's probable that more modern cars have something to prevent this from happening, and my engine is pretty lame, but I thought I'd mention it.
posted by elder18 at 9:38 AM on November 1