Break-in instructions

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")

Thanks!

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

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.

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.

continuously

Just to add a different point of view...

This was a link I found on the i-club forum. Don't have a link to the exact spot though. F.Plant