Break-in instructions

H

H. Whelply

My '04 Forester XT owner's manual says, as do the manuals for any car I've
had, that for the first 1,000 miles the engine shouldn't be run continuously
at the same speed for long periods of time. Can someone explain why that's
bad for a new engine? And how long is a "long period of time"? I'm assuming
that setting cruise control on 75 and staying that way on the open
Interstate for an hour or two would be a "no-no." But what about 30 minutes?
20? 10? Thanks.

HW
 
H. Whelply said:
My '04 Forester XT owner's manual says, as do the manuals for any car I've
had, that for the first 1,000 miles the engine shouldn't be run continuously
at the same speed for long periods of time. Can someone explain why that's
bad for a new engine? And how long is a "long period of time"? I'm assuming
that setting cruise control on 75 and staying that way on the open
Interstate for an hour or two would be a "no-no." But what about 30 minutes?
20? 10? Thanks.

HW

It mostly has to do with wear in of the piston rings to the cylinders.
With freshly machined (i.e., relatively rough) finishes on the mating
parts, initial wear is a lot faster than later after things are worn in
(think of big peaks and valleys rubbing against each other - on a
microscopic scale) to a smoother, and in some senses, a harder surface.

When an engine is running at higher speeds, the parts set up resonances
(vibrations relative to each other on a microscopic scale). At a given
engine speed, the rings will be vibrating (contracting and expanding)
and always hitting or pressing harder on the same places on the cylinder
walls. This can wear grooves in the cylinder walls. Since this is a
relatively rapid wear period (remember microscopic peaks and valleys),
these grooves could become significant during the wear-in period. Now
the normal resonances can get amplified and re-inforced by hitting these
grooves, and the grooves will, in turn, set up new resonances and get
bigger over the life of the engine. That engine will typically have a
shorter life, not be as efficient, and use oil.

By varying the engine speep during the intial wear in period, the points
at which the grooves hit or press hardest against the cylinder walls
during each revolution of the engine get more randomly spread out over
the length of the cylinder wall, so no grooves will form to amplify the
normal resonances.

This is not nearly as critical as it was some years ago, as machining
techniques, tolerances, and surface finishes have improved greatly - so
the "mountains" and "valleys" start out much smaller (effective hardness
is greater and initial wear rates are lower so those grooves are less
likely to form, and the critical wear-in period is much shorter).

Some stop and go and running thru the gears with moderate acceleration
would probably be one of the best things you could do. And when
cruising, just make an effort to continutously vary the speed between
your top cruising speed and maybe 10 or 15 mph below that. Explain to
any passengers what you're doing and why.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")
 
Interesting stuff Bill, glad someone took the time to answer

(Unlike that twat David Betts)
 
Thanks!

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")
 
It mostly has to do with wear in of the piston rings to the cylinders.
With freshly machined (i.e., relatively rough) finishes on the mating
parts, initial wear is a lot faster than later after things are worn in
(think of big peaks and valleys rubbing against each other - on a
microscopic scale) to a smoother, and in some senses, a harder surface.

When an engine is running at higher speeds, the parts set up resonances
(vibrations relative to each other on a microscopic scale). At a given
engine speed, the rings will be vibrating (contracting and expanding)
and always hitting or pressing harder on the same places on the cylinder
walls. This can wear grooves in the cylinder walls. Since this is a
relatively rapid wear period (remember microscopic peaks and valleys),
these grooves could become significant during the wear-in period. Now
the normal resonances can get amplified and re-inforced by hitting these
grooves, and the grooves will, in turn, set up new resonances and get
bigger over the life of the engine. That engine will typically have a
shorter life, not be as efficient, and use oil.

By varying the engine speep during the intial wear in period, the points
at which the grooves hit or press hardest against the cylinder walls
during each revolution of the engine get more randomly spread out over
the length of the cylinder wall, so no grooves will form to amplify the
normal resonances.

This is not nearly as critical as it was some years ago, as machining
techniques, tolerances, and surface finishes have improved greatly - so
the "mountains" and "valleys" start out much smaller (effective hardness
is greater and initial wear rates are lower so those grooves are less
likely to form, and the critical wear-in period is much shorter).

Some stop and go and running thru the gears with moderate acceleration
would probably be one of the best things you could do. And when
cruising, just make an effort to continutously vary the speed between
your top cruising speed and maybe 10 or 15 mph below that. Explain to
any passengers what you're doing and why.




OUCH!!!! i wonder then, when you buy from the dealer, and he NEVER has
the car on the lot, and someone drives the car back to your dealer for
your pick-up. You have no control over how the milage is put on the
car. and do you REALLY think they give a crap about your break in
period? you wont even know there was a problem for years.
 
OUCH!!!! i wonder then, when you buy from the dealer, and he NEVER has
the car on the lot, and someone drives the car back to your dealer for
your pick-up. You have no control over how the milage is put on the
car. and do you REALLY think they give a crap about your break in
period? you wont even know there was a problem for years.

Exactly. Saturday, I'd just about agreed to a silver Forester XT
(non-Premium) that I was told already had about 120 miles on it. It
was the closest they could come to my spec. They seemed to think this
was no big deal, the 120 miles; most of their cars on the lot had 20
or more miles from demos. In fact, on my test drive in July, the sales
person encouraged me to stomp it to experience the power. I just
couldn't do it.

Back to the sales story....The dealer needed to swap one of his XT
Premiums for it, saying "my" car would be brought in from a dealer
about 45 minutes away. The car would have had probably in excess of
200 miles on it. (I'd pressed for location, and that's all they'd tell
me--45 minutes. Knowing the area, and dealer locations, I suspect it
was actually farther away.) But the sales manager didn't like losing a
Premium model (and higher profit potential, no doubt), and offered me
a Premium very close to my spec in my preferred white for only $1,100
more than the price he'd quoted on the silver one (normally an
additional cost of $1,800). I looked at the car, which had just come
it and had just been prepped. It was beautiful, and the odometer read
"3"--just three miles. That sold me more than the leather and sunroof.
By the time they'd put gas in it, I drove away with a car that had
been driven 5 miles. Of course, I don't know how it was driven those
few miles, but the probability of abuse seems much diminished.
 
Hi,
Car transporter can bring the car to the dealer from else where. It does
not have to be driven. Both of my kids' Impreza when bought came from
out of town, one was about 200 miles away, one was 400 miles away.
(because of options, color choices, etc., etc.)
Both were brought in by transporter. In this case, odometer reading is
near zero. I saw them being unloaded at the dealer lot.
Been to whole sale car auctions for dealers only? Every week, many cars
move in and out of every direction by transporters from the auction lot.
Tony
 
Tony Hwang said:
Hi,
Car transporter can bring the car to the dealer from else where. It does
not have to be driven...

In this particular case, I asked specifically about who would be
driving the car, and was given a description. No question about it, in
this case: the car would be driven, not placed on a transporter.
 
Bill's advice is good and matches what my local Subaru service manager
said in term of why break in is important.

I suspect everyone agrees that people have different ideas about what
break-in is necessary. The manual says one thing, service managers
say another, you have friends that do this or that...

So with that in mind, here is my experience. I have a 2004 Forester
XT. I got it with about 15 miles, drove it convervatively for about
50 miles, and then went to talk to a Subaru service manager who had
been in the industry for 20+ years. He said to drive the car in the
break-in like you plan on driving the car during its lifetime. He
Subarus can take pretty much whatever you tell them to do -- his only
caution was not to try to rev the rpms and drove it into 1st for a
squealing start -- he said to let the engine do the work, not the
tranmission. He said if you baby the car during the break-in, you
might not get the engine to perform as well later in life.

You are looking at a bit of a trade-off when you talk about driving
habits (generally speaking, not just during the break-in). Drive it
hard all the time and you will shorten the life of your engine...
though I would ask this: why buy a Forester XT if you don't like to
really drive? I would say the key is to drive responsibly and know
your limits. I've also heard that you should let the turbo cool down
for 30 seconds or so before shutting of the engine.

My decision on how to drive since then? My last few hundred miles
have been pretty much all city driving -- generally with brisk
acceleration, with a few full accelerations on occasion.

David
 
H. Whelply said:
My '04 Forester XT owner's manual says, as do the manuals for any car I've
had, that for the first 1,000 miles the engine shouldn't be run continuously
at the same speed for long periods of time. Can someone explain why that's
bad for a new engine? And how long is a "long period of time"? I'm assuming
that setting cruise control on 75 and staying that way on the open
Interstate for an hour or two would be a "no-no." But what about 30 minutes?
20? 10? Thanks.

Just to add a different point of view...
http://www.mototuneusa.com/break_in_secrets.htm

This was a link I found on the i-club forum. Don't have a link to the exact
spot though.
http://www.i-club.com/forums/index.php?s=

F.Plant
 

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