What do I do with a brand-new car?
April 9, 2012 2:30 PM   Subscribe

How do you "break in" a new car?

I am about to buy a new car, which I've never done before, and I'm wondering if there is anything specific I should do to break it in? Is that necessary? I have googled and gotten a lot of conflicting information. It'll be an automatic, if that matters.
posted by feathermeat to Travel & Transportation (19 answers total) 7 users marked this as a favorite
Check your manual first. My car's manual explicitly has a section saying, basically, "Don't do any of that weird voodoo stuff to break it in, just drive it like normal."
posted by Ghostride The Whip at 2:36 PM on April 9, 2012 [1 favorite]

Modern cars don't demand as much special care as their older fore-fathers.

I think my only advice would be to take it easy on the thing and change the oil sooner than you otherwise might (whatever friction and/or break-in takes place might create itsy bitsy particles that could cause more damage if they stay put). Then keep synthetic oil in it.

Short answer: Nothing fancy
posted by milqman at 2:39 PM on April 9, 2012

I know on the 3-series BMW, you are not supposed to "floor it" until you reach something like 1500-2000 miles. (check the Owner's Manual) This is supposedly to give the gaskets time to 'properly seat' or something like that. In addition, you are supposed to vary the speeds and not drive extended distances using cruise control.
posted by dcjd at 2:43 PM on April 9, 2012

Check the fluids, air filter and tire pressure. Otherwise, nothing fancy.
posted by Cool Papa Bell at 2:46 PM on April 9, 2012

You should read the break-in section of the manual and do exactly what it says there, I reckon.

Some people swear by changing the oil after 500 miles, but that wasn't in my manual, so...
posted by Juffo-Wup at 2:47 PM on April 9, 2012 [3 favorites]

Road trip! I always try to do a shakedown cruise in any new car.
posted by XMLicious at 2:50 PM on April 9, 2012

Do as the manual says, and make damn sure that you get it's first scheduled service done on time/mileage (whichever comes first). The first service is critical to both checking that everything is starting to wear properly, seat itself in, etc. and to correcting problems early if they're starting to occur.
posted by Ahab at 2:51 PM on April 9, 2012 [1 favorite]

1) Follow the manual and scheduled service. Just bought a new car and they included the first oil change in order to check everything over at that point and told me when subsequent oil changes should be.
2) I've also made a point of regularly scheduling cleaning/car washes in my calendar with my new car. I wasn't as good about it with my old car, but I want to keep this one looking as new as possible for as long as possible.
3) Park in the middle of the parking lot and get your first door ding. (Yeah, I was super sad about this. So you can be a typical new-car-owner and park 8 miles from the grocery store door and I won't hold it against you.)
4) Road trip!
posted by sararah at 3:02 PM on April 9, 2012

Arg, didn't mean to hit post so soon.

I usually take a drive on a long stretch of road that doesn't have that much traffic.
posted by littlesq at 3:17 PM on April 9, 2012

Conventional wisdom says no road trip before about 600-1000 miles. Or your first service.

In any internal combustion engine, new or old, the pistons (or their rings) are packed tight into the cylinders when new. The piston rings aren't quite a perfect fit at every point of their circumferences as they slide up and down their (eg vertical but it aint always so) journey within the cylinder. So if you go on a long high speed journey, they will heat up and try to expand beyond the internal diameter of the cylinder. Then as they ram up and down, they'll hit points on the cylinder wall that are narrower than the (enlarged while hot) diameter of the rings. This can seize and/or break stuff.

Rather than have that happen, you drive around for 1000 miles or so letting the piston rings and the cylinders expand and find their points of closest contact, and wear away at each other just a little at those points, in exactly the places where they need to. Then when you do run it hard and hot, everything is bedded in, slams up and down nice and comfortably, and nothing seizes or breaks.

Similar problems apply to cams and valves and stuff inside auto transmissions. Early on, take it easy and try to stick to short to moderate length journeys at moderate speed.

Conventional wisdom on the early oil change (and filter clean or replacement) is that your engine will run hotter than normal early on. This runs the risk of burning the oil, or just heating it enough to reduce it's lubricating capacity. That in turn means your engine runs hotter still, etc.. Also, the bedding in process wears away a fair bit of metal. That goes spinning around in your engine acting as an abrasive and wearing things out faster than it should (oil and tranny fluid filters first, then other stuff).
posted by Ahab at 3:21 PM on April 9, 2012 [5 favorites]

Sorry to come back a third time. dcjd is right about the gaskets up there as well. Lots of gaskets in modern vehicles are self sealing. They're made of an absorbent material that soaks up a little bit of whatever fluid they're meant to contain. That absorption pads out the inner fraction of the gasket and creates the seal. The nuts/bolts/screws (etc) that hold the parts either side of the gasket in place are deliberately left just a fraction looser than they will be after the car is run in and the gasket has soaked up some fluid, or after they are tightened slightly at your first service. If you drive fast and hot early on, you run the risk of creating too much heat or pressure on the inside edge of the gasket. This can cause fluid to leak around the gasket before it has soaked enough fluid up to seal properly, cause the gasket to soak up fluid unevenly (creating a channel for leakage and making it difficult to evenly tighten nuts/bolts/screws etc), or cause it it to soak up too much fluid all around which can damage the gasket or create multiple channels for leakage.
posted by Ahab at 3:53 PM on April 9, 2012

I have a friend who's an automotive engineer. He summed up his experience once by saying, "never buy a first-run car." So, if you have a first-run car (i.e. not one that's been in production for a few years or whatever), pay more attention to the advice already given here.
posted by circular at 3:55 PM on April 9, 2012

It used to be that an engine needed to be 'run-in' due to imprecise tolerances and (relatively) poor quality oils.

Modern manufacturing means that tolerances are much more accurate and oils with much better lubricating properties (ie synthetic) mean that, apart from an early service that manufacturers generally schedule for somewhere around 1,000 km to and generally being alert to any strange noises or behaviour, you don't need to do anything special. The same things that you should do to make your car last longer (driving smoothly, regular maintenance etc) are the same things that you should be doing from day one. The first service may include things like checking the tension on head studs etc to take account of normal stretching, so it's probably a good idea to take it fairly easy until that point in case of anything that needs attention, though.

The most important thing is the keep the windows closed as much as possible to trap that 'new car smell' ;-)
posted by dg at 4:02 PM on April 9, 2012

My owner's manual's only advice about the break-in period was I needed to keep the speed under 80% of the maximum value shown on the speedometer. Since it went to 160mph that meant I had to keep it under 128 mph which I managed to do.
posted by birdherder at 4:07 PM on April 9, 2012 [2 favorites]

Buy a can of Scotchgard (or a similar protectant, though I've liked the original 3M stuff) and give at least the front seats a thorough spraying before they get dirty from use. It'll make them much easier to clean and more stain/spill-resistant for the first few years you own the car. Depending on how obsessive you are, you can also Scotchgard back seats and floor mats, Armor-All exposed interior plastic, Rain-X windows, and so on ad infinitum, but getting some stain protection on the front seats seems like a good minimal, non-OCD measure of initial care-taking.

The mechanical stuff has been well covered already, but just to reiterate, the basics are (1) follow the manual, (2) don't do anything fancy or superstitious, but do try not to rev it too hard for the first few hundred miles.
posted by RogerB at 4:55 PM on April 9, 2012 [2 favorites]

I just bought a new car myself, and did a hybrid of the various conventional wisdoms. (Which I have done on other new cars that I've bought, and had success with.)

First, I made very sure to keep an eye on all the fluids to make sure there weren't any leaks going on.

Second, I did exactly what the manual said to do, which is probably mostly the same for most normal cars. Don't drive it hard, don't maintain steady RPMs, etc.

Third, after that period was over, I changed the oil, and proceeded to drive it like I stole it. After that period, I always felt like the engine ran a little smoother and stronger, but that may well be confirmation bias.

Fourth, at the first recommended oil change, I switched to Mobil 1 synthetic. I'm aware of all the arguments for and against it, and my experience has been that even if it doesn't do any good for the car, it for sure doesn't do any harm, and it gives me peace of mind. On all the cars that I've had where I've run synthetic from the beginning, the engines have performed flawlessly until the day I traded them in. Still had all the power they always had, passed emissions with flying colors, etc. When I look into the oil fill hole, there is no varnishing or obvious wear. (And this has not been true for other cars I've seen that didn't run synthetic.)

Fifth, my owner's manual actually suggests running some Techron (or similar) every 3000 miles or so. Sure enough, after about 5000 miles, I noticed a little hesitation on acceleration. Ran some cleaner and it fixed it right up. So if your manual says that, it's probably a good idea to pay attention to it.
posted by gjc at 6:03 PM on April 9, 2012

There are two consistent rules I've seen.

First, not maintaining a constant engine speed for long periods of time. Now, what that means is no road trips maintaining the same speed for 4-5 hour stretches - Don't stress over any commute that happens to have a stretch on the expressway.

The other thing - As far as keeping it below 80% of speed during break in, the way I have seen that is under 80% of ENGINE speed - i.e. 80% of redline. That being said, I redlined a vehicle multiple times during the test drive (once it warmed up), bought it, and put 120k miles on it with no engine issues whatsoever.

The reality of it is that you should do what your manual says, and don't drive like a jackass, and don't worry about the details so much. If you overthink this, you'll spend 600-1000 miles developing an ulcer. Unless you are buying an exotic, this simply isn't the issue it used to be. Do sane things like not redlining it when the engine is cold and you'll be fine. Drive it normally, don't sweat it, and enjoy having a new car. I've broken in several vehicles, and I've never once had an issue, even when I didn't know what the hell I was doing.
posted by MysticMCJ at 8:23 PM on April 9, 2012

Whatever you do, the effects won't show up for another 150,000 miles or more, and nothing will show up on dealer checkups. Just drive normally. If you are paranoid, get an early oil change. Break in isn't really a thing these days.
posted by colinshark at 8:44 PM on April 9, 2012

The piston rings aren't quite a perfect fit at every point of their circumferences as they slide up and down their (eg vertical but it aint always so) journey within the cylinder. So if you go on a long high speed journey, they will heat up and try to expand beyond the internal diameter of the cylinder. Then as they ram up and down, they'll hit points on the cylinder wall that are narrower than the (enlarged while hot) diameter of the rings. This can seize and/or break stuff.

This is neither true in isolation, nor the issue with prolonged constant speed running on new engines/pistons rings. There is no 'overheating to cause expansion past the cylinder walls dimensions' and this won't cause your engine to seize - this is misleading and a little over-dramatic as running and engine in badly is unlikely to actually cause an engine failure, just potentially reduce its efficiency and maybe knock 5-10,000 miles of the far end of its life.

The reason that you try to avoid cruising or long steady speed runs on a fresh engine is that the piston bores can become glazed by a very narrow load style and smooth the bore walls off. They tend to get shiny and look a bit like a mirror (I've seen this on dyno'd engines). This will allow a difficult seal between the rings and the pistons and promote higher oil consumption (oil coming up past the side of the piston) or low efficiency (gas blowing past the sides of the cylinder on power). It can also create more friction and heat/wear because the usual slightly..... scratched, I guess, look to the piston bore holds oil better and also has less of a contact patch with the ring itself so is less friction inducing. It won't seize your engine, though, it will just wear the rings to the same point of poor sealing and high oil consumption. It is best to vary the load case of the engine during the first 1000-1500 miles to make sure you get a decent break-in of your pistons and rings in the bores.

In other driving, if you just drive normally, you're probably doing everything you already need to do. Hard driving (prolonged acceleration or full throttle and high rev driving) should be avoided, but as mentioned above, full load acceleration (low revs, floor it to about 75% of your rev limit) actually help to seat the piston rings and avoid the glazing mentioned above.
posted by Brockles at 8:22 AM on April 10, 2012

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