how to properly break in a new car

[KnifeEdge_2K1]

ive heard two distinctly different and opposite theories for the break in process

one is run it hard (lots of full throttle accelerations basically driving like you stole it) for only a short time (couple hundred miles)

and the other the more conventional
run it easy, never go more then 1/4 throttle dont pass 3000rpm for about 1000km

what's common to both methods is never staying at a constant speed/gear/or throttle position, letting it rev up and down so that the internals (piston rings, bearings, etc.) to seal properly

i was just wondering which method most of you guys use

i'm probably going to go for the more conventional method, no full throttle accelerations for first 1000 or so kms

[Equinox]

conventional method...

and when i first read the title and the first line i thought this was a thread on how to break into a car and steal it

then the second line threw me off, then i got it!

[TheOne]

most of it is to try to get seals and everything to fit in, which just means not to run the car @ certain rpm for a long period of time, just rev up and down, that will wear the rings in and seal propertly, and probably most other things inside an engine.

[Egg Nog]

This is a pretty interesting article. A lot of it makes sense, but it does beg the question "then why have the factories all specified it differently".

http://www.mototuneusa.com/break_in_secrets.htm

[NAASBC355]

well I have had an experiance lately that was somewhat odd. If the motor uses synthetic oil apparently you have to be harder on it to get the rings to seat, but being an engine builder I say let it smoke for at least a 1000 miles if you have to before you are hard on it. My concern is the bearings: bearings have to harden to be able to take the abuse that they under go. They will infact become harder than the crankshaft in some cases, but it takes about a thousand miles or so for the bearings to fully break in. In my case it was a chrome ring in a race motor that still hadn't seated in 5000 miles. The customer called me to complain and when i found out he had been running mobil 1 the whole time, I told him to go beat the tar out of it, and the rings finnaly seated. Never break in a motor on synthetic oil by the way.

~Couch

[clutch-monkey]

Originally Posted by NAASBC355

Never break in a motor on synthetic oil by the way.

~Couch

thanks for the warning
edit: not that i'll ever have a brand new car anyway lol

[charged]

When I was working at Cummins diesel as a mechanic, after we rebuilt the motor we would run it WOT and load the engine down to 1200 rpm to bed the rings in. When we run our rebuilt race engines we run them at 9psi for 10 mins, then we run them at 24 psi for some full power runs on non synthetic, change the oil to Mobil 1 and then they are ready for the track

[hightower99]

Originally Posted by Egg Nog

This is a pretty interesting article. A lot of it makes sense, but it does beg the question "then why have the factories all specified it differently".

http://www.mototuneusa.com/break_in_secrets.htm

I believe this is the correct way to break in an engine. It makes perfect sense and he tells you everything including the answer to "why do the factories say differently?"

Answer: Because they think like this: People always have a learning curve when they start using a new vehicle and if they told you to go at it WOT up and down the rev range then this would increase the number of accidents and would open an opportunity for people to sue the company. So most vehicles are at least partially broke in with WOT at the factory and they tell you to take it easy for the first 600-1000miles. simple really.

[KnifeEdge_2K1]

Originally Posted by Egg Nog

This is a pretty interesting article. A lot of it makes sense, but it does beg the question "then why have the factories all specified it differently".

http://www.mototuneusa.com/break_in_secrets.htm

haha thats the one i was reading !!

i'm so confused :S:S:S

i figure im just gonna take it up and down the rev range quite a bit for the recommended break in period, probably gonna pass the 1/4 throttle mark as the car has a tiny lil 1.5L engine

gonna avoid full throttles though as the thought of it makes me soil myself

[KnifeEdge_2K1]

Originally Posted by NAASBC355

Never break in a motor on synthetic oil by the way.

~Couch

wut's the difference between breaking in on synthetic and petroleum ?

[Quiggs]

I've always believed it's best to break it in how you plan on using it. If you're going to granny it around normally, granny it while you're breaking it in. If you're going to beat it every day, beat it from day one.

[Equinox]

this is all messed up... i'm just going to buy a used car... no worries!

[TheOne]

yes, it is better to break in an engine with dyno oil than synthetic, don't remember the reason behind it but i've been told by many engine builders, also to not keep revs at a certain rpm for long periods as that wont break in the piston rings right.

and to change the oil a couple of times(ie after a couple of miles of bein rebuilt, after 500 miles and after 1000 miles to take any metal shavings, which there shouldn't be any if you propertly broke it in)

[h00t_h00t]

I don't really understand that article, he implys that the cylinders are expertly honed but the piston rings are more of a poorly made after thought. If engines are as well made as he suggests then it shouldn't need to be broken in.

[KnifeEdge_2K1]

Originally Posted by h00t_h00t

I don't really understand that article, he implys that the cylinders are expertly honed but the piston rings are more of a poorly made after thought. If engines are as well made as he suggests then it shouldn't need to be broken in.

they arnt perfectly honed, they have a patern built onto them to allow the rings and pistons to wear each other down allowing the rings to seat properly

manufacturing process inevitibly creates parts which have small inconsistencies to the original design, this is why an engine needs to be broken in

the question is, what's the best way to get the rings to properly seat, and the window of time that you can do this