Engine Break in - 3.6L Pentastar

[1quick1]

I tried to change revs on mine as much as possible. It has just over 400 miles on it so I'm sure it's good to go by now for the highway.

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[Capricorn]

It is easier to vary RPMs with a manual while driving moderately. Very hard to do it on an 8 speed automatic while cruising.

 

[Adventure.AS]

It is easier to vary RPMs with a manual while driving moderately. Very hard to do it on an 8 speed automatic while cruising.

AutoStick works great for up and down shifting the 8-speed automatic.

 

[Capricorn]

AutoStick works great for up and down shifting the 8-speed automatic.

True.

 

[RV Wrench]

Drive it like you stole it; best break-in, period. Rings seat better/quicker=less blow-by=less harmful stuff ends up in the oil. Has anyone ever been lectured by a Jeep salesman about this "proper break-in" before a test-drive? If it were really that critical, they would have all their sales guys lecturing you and having you sign a notification before test drive that you wont exceed the parameters. But they don't. They stick that info in the "owners manual" so that once you are the owner and something breaks, they have a leg to stand on to deny a warranty claim. You know, like these engine leaking and ticking threads posted in the forum...

That being said, my JL had 450 miles on the ODO when I got it; already "broke in" by test-drivers.

 

[Cwg33]

Drive it like you stole it; best break-in, period. Rings seat better/quicker=less blow-by=less harmful stuff ends up in the oil. Has anyone ever been lectured by a Jeep salesman about this "proper break-in" before a test-drive? If it were really that critical, they would have all their sales guys lecturing you and having you sign a notification before test drive that you wont exceed the parameters. But they don't. They stick that info in the "owners manual" so that once you are the owner and something breaks, they have a leg to stand on to deny a warranty claim. You know, like these engine leaking and ticking threads posted in the forum...

That being said, my JL had 450 miles on the ODO when I got it; already "broke in" by test-drivers.

Agreed. That is lawyers throwing in data for risk avoidance. Yamaha has always had the same 10 hours under 2000 rpm BS on every 125, 250, ATV, etc., and I’ve always varied revs during break-in up to 6000rpm. Still have a 2010 with 100’s of hours, and no rebuilds ever needed. The last thing I would do during break-in would be keep rpms low, and stay at 50-55mph. If you’re in town, bomb starts up to 4000rpm. On Highways, squeal tires to get to speed. Did this on my last 4 Wranglers, and never had oil burning, even on 2 notorious 3.8 oil burners.

 

[smokeythecat]

(to be clear, I get frustrated with people relying on anecdotal evidence to tell others to ignore the manufacturer’s advice, not the people who in ignorance don’t follow it)

I just took delivery of my very first Jeep today (2-door Wrangler, Willys trim) and I fully intend to follow the manufacturer's advice. However, I'm a bit peeved at the ambiguity of the working. I supposed I can guess/intuit what "moderate" means, but does the second sentence mean I shouldn't be driving it on the freeway or at freeway speeds until after the first 60 miles?

 

[Capricorn]

I just took delivery of my very first Jeep today (2-door Wrangler, Willys trim) and I fully intend to follow the manufacturer's advice. However, I'm a bit peeved at the ambiguity of the working. I supposed I can guess/intuit what "moderate" means, but does the second sentence mean I shouldn't be driving it on the freeway or at freeway speeds until after the first 60 miles?

I had the same question.
It doesn't specifically say also how to drive in the first 60 miles different from 60 - 300 miles.
I treat the first 0 - 60 miles the same as 60 - 300 miles.

Also read the break-in recommendation from other manufacturers. Jeep's gas engine is not uniquely different from other ones. The common theme is to vary the speeds or RPM, do not WOT from stand still, avoid hard braking, no cruise control, no towing etc. Avoid exceeding 4000 rpm.

 

[zakaron]

The recommendation of not driving at highway speed for the first 60 miles is more for the differentials and to keep them from overheating since they are still breaking in and create the most frictional heat during this time. That was a big run-on sentence…

 

[Kreepin1]

The recommendation of not driving at highway speed for the first 60 miles is more for the differentials and to keep them from overheating since they are still breaking in and create the most frictional heat during this time. That was a big run-on sentence…

It might be run-on but it is correct because while most folks focus on the engine they forget that differential break-in is also important as is breaking in the brakes to a lesser extent. There, feel better about your sentence now?

Regarding engine break-in I had a Professor of Metallurgy explain it to me this way. There are tiny high spots on the cylinder walls from the machining process. As you increase throttle you also increase how hard the piston's rings press against the cylinder wall. The best way to break in an engine is with short bursts of acceleration followed by taking your foot off the accelerator. Under accelerations the high spots to start to melt, forming little mushrooms. When you take your foot off the gas the vacuum in the combustion chamber sucks oil past the rings cooling them so they snap off during the next pass of the rings.

Hot rodders have a saying "an engine broken in hard will run hard." This makes sense as the drag strip seems like an almost ideal way to break in an engine. Full throttle blasts 10-15 seconds long followed by taking your foot completely off the accelerator.

When I break in an engine I start with 3/4 throttle for 3-5 seconds at a moderate rpm. I gradually increase the length of the pull, the amount of throttle, and the maximum rpm I hit. After 20 minutes or so I stop for lunch and let the differential cool off. Typically three heat cycles and the differential is good to go. Someday I'll try to explain to a police officer what I'm doing. "jHonestly Sir, I'm just trying to properly break in the engine on this new Vette..."

 

[XtremeRetard]

It is easier to vary RPMs with a manual while driving moderately. Very hard to do it on an 8 speed automatic while cruising.

Bringing this back from the dead. Just to say the best method I have found is to set cruise on the highway and manually shift the autotrans, speed stays the same, but revs go where ever you want.

 

[demarpaint]

We just bought a Wrangler JLU Sahara for my wife's b-day. This is the first Wrangler we have owned and we are both in love with it. There were 34 miles on it when we bought it 2 days ago and now there are 172. Obviously we are in the break in period for the engine and obviously I am a dumba$$. I love muscle cars and Jeeps and anything with horsepower.
While test driving this Jeep I dropped the hammer on the pedal and was surprised and how this engine moves 4,400 lbs so easily and quickly. And that is my weakness, I love to drop the hammer. So now I am freaking out because I forgot "Hey idiot, you are in the break in phase!!!!". In the last 135 miles or so I have dropped the hammer about 10 times (yes I actually tried to remember exactly how many). Then I went on the web and looked up the best way to break in an engine...
1. DON'T DROP THE HAMMER
2. DON'T GO ABOVE 4,000 RPMS
3. Vary your speed and loads
4. No cruise control
5. Don't tow

So I've broken the first two rules about 10 - 12 times in 135 miles. Break in periods typically are anywhere from 300 to 1000 miles. Obviously I won't be dropping the hammer anymore and I will obey the break in laws. Anyone have any opinions on any damage (hot spots, wearing the rings too fast, etc...) I might have done? We plan on keeping this Jeep a LONG time and I now that now is the time to get it right.

I also plan on using the same Penzoil Platinum 0w - 20 that it shipped from the factory with and Mopar filters for my oil changes. I most likely will go less than the 7,500 miles between changes and also plan on doing a change around 750 miles to flush out any break in particulate.

Having sold cars for a few years I can tell you, the lot boys beat the hell out of vehicles just moving them around the lot. So dropping the hammer a few times is not going to hurt the engine much. I won't go into how I was taught to break in an engine, that can become as heated a discussion as what oil/grade do you use. Having said that during break in I make sure the engine has been running at least 30 minutes +/- so the oil is up to full operating temperature before I get on it.

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