Lone Ranger

I am a believer in breaking in a new engine using a specific technique to ensure optimum seating of the piston rings. It is fairly simple. the theory is you want to achieve maximum cylinder pressure when the engine is new, in order to seat the rings, but you do not want to over rev the rpm's beyond 75% of tachometer redline. So if your tach's redline is marked as, say, 6000rpm 75% of that is your max rpm threshold during break-in for the first 1000 miles (4500rpm). During the first 1000 miles I accelerate strong and brisk, but let off before the needle exceeds 75% rpm threshold on the tach. Of course this is hell on MPG during the break-in period, but I believe it pays off over the life of the vehicle in minimal oil consumption and optimal fuel economy and power.

I've broken in all my vehicles this way and they always proved to be very low to neglible oil consumption between oil changes, and returned good power and mpg for their model. Except for a 1994 Dodge truck I bought new, which I am convinced uses a quart of oil between changes simply because its a Chrysler product.

I believe the last thing you want to do is baby the new vehicle during the first 1000 miles.

Don't have a Forester yet, but if I get one, this is probably how I'll break it in.

RocketEyes

My tuner agrees with you. Not sure how many on here will.

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Meg
2007 WRB XT Sport Auto

Lone Ranger

Attaining maximum cylinder pressure during break-in is even more crucial on a forced induction motor (turbo or sc) due to the piston rings usually being more robust in order to handle the boost.

The Black Box

Amazing. That's exactly what the manual recommends! Don't forget to vary engine speeds.

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'08 XT LTD/MT

Peaty

I went easy on my car for the first 1K miles. I don't burn oil and at 80K my oil analysis shows my motor is in excellent shape. I followed the owners manual recommendations.

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Peaty

04 -XT

06 B9 Tribeca & 99 Miata

ScoobyMods

peatpics

Panos

So far i have around 450 miles on my Forester. I take it up to about 4000RPM's then back off the throttle so it shifts right around 4000RPM's. I don't do it all the time though, just a couple times during every ride i take it on. I'll do it more as the engine climbs towards the 1000 miles mark.

Of course this is a topic that has been beaten to death. Some people believe you should "drive it like you stole it" right off the showroom floor and others will say to baby the hell out of it until after 1000 miles....I think the method above with a few brisk runs up too 4000-4500RPM's every once and a while is a good way to break in a new engine. Just don't floor the gas pedal.

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09' Spark Silver 2.5X Premium

stan_t

This is a controversial subject. What are your thought on when to change the oil for the first time, and if/when to switch to synthetic? Always makes for a fun discussion

I also make sure to break in the rings ASAP.

Stan

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'07 XT 5MT, VF43 tuned by FLI
handling > power > looks

vintage42

I would only add one thing. The more frequently the strong and brisk acceleration is done, the better. This is the essence of the "varied speed", where it is the variations or transitions between speed that are important, not the speeds per se. So driving vigorously on twisty hilly country roads is the best and most fun way to do a break in -- constantly on and off the throttle, rocking the engine and drive train between acceleration and deceleration. I have used Lone Ranger's technique on many rebuilt vintage motorcycles and all my cars. It is what the Owner Manuals intend but cannot dictate because most people can't devote their life to the break in.

With cars, the break in is not critical, as the motors will do OK if they are driven any way within reason. But a good break in will result in an engine that is optimized.

With the bikes, the critical difference can be apparent. Too gentle, and the rings don't seat and the bike blows and burns oil. Too hard, and the pistons seize.

Integrity Performance

pghul1

Apparently, engine braking (deceleration) is just as important (more?) as acceleration in settling the rings, as more load is placed on the rings etc during deceleration.

The first twenty miles are critical for settling the rings.

Cheers

vintage42

Yes, every acceleration cannot help but be followed by a deceleration, to maintain the speed and rpm limits of the break in. But on a modern car, the break in is not critical. As long as the engines are not abused, they get by, at least through the warranty period.

snaker

My brother is an automotive engineer & he says that most newer engines are put through a break in cycle at the factory & you mainly have to worry about breaking in the clutch & brakes for the 1st 4-500 miles. But he says break in a new engine he would get on the highway & short shift into 3rd gear and give it full throttle up to almost redline and coast back down & pull over & let t cool down or 15 - 30 minutes & Repeat 4 times. Go home & change the oil & then run it normally so the computer learns your driving habits.

He Says it worked on all of his test engines at Kettering University.

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2007 Forester 2.5 XT Stage II

snaker

Yes, after about the 1st 20 miles, the crosshatches in the cylinder walls are smoothed out so they will be less abbraisive after that. (I can't spell)

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2007 Forester 2.5 XT Stage II

SuperTurbo

The truth on break in is to drive as fast as you can afford with the lowest gear possibile.
Do more sudden acceleration & engine brake!

vintage42

I just toured the Subaru plant in LaFayette and they don't "break in" engines, and I doubt that any other manufacturers do, either. The time and labor would be cost prohibitive.

The engine is started and run long enough for the ECU to go out of safe mode and begin running on sensor feedback, then the car is driven a hundred feet to a transmission testing and setting station and then to a final quality check station. The stations have rollers and the engine is revved up and down through the gears. Then the car gets a short drive over the bump section of a test track before being parked on the big lot. That is the extent of any Subaru factory break in.