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When's the 3.6L broken in?

nU7OuxIx

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I have a feeling that it's just a guess, but I was wondering about what mileage is the engine finished with the break-in schedule? I *thought* it used to be like 3,000 miles, but that may be an old number to go by. The book mentions 300 miles, but doesn't really say if that's when you're good to go with everything normal (highway driving, towing, etc) or if that just means continue driving moderately.

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jonahgetz

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The Jeep manual covers all the details. I drove the first 300 miles under 55mph and low RPM, after 300 miles I started to do a light acceleration every once in a while at various speeds. I think at 350 miles was when I first went on the freeway and took it up to 75mph. I never really allowed the RPMs to go above 4-5k. I waited till about 1000 miles before I tried a full accelerations and revved to red line before shifting, started with 1st gear through 4th. I was curious to see the pull. I don't rev past 2500 RPMS now, I'm at 5200 miles. I've learned that if you rev high you start to see the mpg plummet.

My biggest scare was around 220 miles I had to help my buddy that got stuck in the sand out in the middle of nowhere. I had to rev pretty high to get the torque to pull his chevy s10, and it still wasn't enough so I gave up and 2 hours later a diesel found us. After that incident I was uneasy, I started to go through all the scenarios in my head of how I could of just did permanent damage, or premature wear. I guess time will tell how many miles I get out of this motor. Sometimes life just happens and I really wanted to help my buddy out.
 
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nU7OuxIx

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The Jeep manual covers all the details. I drove the first 300 miles under 55mph and low RPM, after 300 miles I started to do a light acceleration every once in a while at various speeds. I think at 350 miles was when I first went on the freeway and took it up to 75mph. I never really allowed the RPMs to go above 4-5k. I waited till about 1000 miles before I tried a full accelerations and revved to red line before shifting, started with 1st gear through 4th. I was curious to see the pull. I don't rev past 2500 RPMS now, I'm at 5200 miles. I've learned that if you rev high you start to see the mpg plummet.

My biggest scare was around 220 miles I had to help my buddy that got stuck in the sand out in the middle of nowhere. I had to rev pretty high to get the torque to pull his chevy s10, and it still wasn't enough so I gave up and 2 hours later a diesel found us. After that incident I was uneasy, I started to go through all the scenarios in my head of how I could of just did permanent damage, or premature wear. I guess time will tell how many miles I get out of this motor. Sometimes life just happens and I really wanted to help my buddy out.
Everybody view on the break-in is different. Some say rev it up and be heavy on the gas. Others say baby it. In the end, I don't know if there's necessarily a right or wrong way to break it in.

I followed what the manual said. Unfortunately though, they just really mention the 300 mile point and nothing after that. I have a short trip planned tomorrow (~hour drive on the expressway) and was wondering at what point can I stop thinking about the break-in period.
 

jonahgetz

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Everybody view on the break-in is different. Some say rev it up and be heavy on the gas. Others say baby it. In the end, I don't know if there's necessarily a right or wrong way to break it in.

I followed what the manual said. Unfortunately though, they just really mention the 300 mile point and nothing after that. I have a short trip planned tomorrow (~hour drive on the expressway) and was wondering at what point can I stop thinking about the break-in period.
How many miles are you currently at?
Maybe a few more people will chime in with their 2 cents, I'm interested to see what others will say.
 
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nU7OuxIx

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How many miles are you currently at?
Maybe a few more people will chime in with their 2 cents, I'm interested to see what others will say.
If I were to guess, I would guess 350ish miles. Since working from home, I don't drive nearly as much as I used to.
 

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If I were to guess, I would guess 350ish miles. Since working from home, I don't drive nearly as much as I used to.
Oh I would absolutely take it on the freeway or motorway at that point. After 300 miles I was off-roading and driving on the freeway. I'm at 5200 miles now and everything feels/sounds good.
 

AZ Great White

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I bought mine at a Lake Havasu , AZ dealer 200 miles from home so it got broke in on I-40. First 100 miles I kept the speed around 65 mph or so but after that I got tired of the semi’s passing me at 80 mph so as a safety factor I kick it up to 75 mph. 800 miles on the clock and on issue so far!
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I took it on the freeway and went 80 when it had 12miles. If you wanna be ultra careful, all you have to do is not rev it above 4K until she’s around 500-600miles on the odo. Modern engines need very little break in, if at all. And be the time most people get their Jeep’s, it’s already too late anyway as the first 5-10miles is what matters most, but even then it still matters very little in the overall picture.
 

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This is an easy one. You are all wrong.

The engine is broken in when the rear main seal starts to leak. Could be anywhere between 5,000 and 25,000 miles depending on (1) how bad a day the person who put your engine together was having, and/or (2) whether your trusted and knowledgeable Jeep dealer filled it up with 6 quarts of oil instead of 5 for that "free" oil change.

Just take a look underneath your rig and notice the two "Regret Holes" on the bottom of the engine near the oil pan and transmission juncture. Visually inspect and even better stick a finger up there and then crack a smile with delight at your engine broken-in-ness when you feel the oil leak!

Jeep Wrangler JL When's the 3.6L broken in? 1619480602763
 

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Modern engines need very little break in, if at all.
It's not just the engine that needs breaking in. All moving parts in the drive train and braking systems are involved. The Owner's Manual tells you what to do.
 

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MtnJeep

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When it shows up it will just get driven normally from day one. So many theories, so many misconceptions. I think that it is total luck of the draw to get a bad one and doesn't have anything to do with how you "break it in". Unless you drive it off the lot and into competition, it isn't really going to matter. I remember having a high performance engine built for my old Buick, spent a lot of money on it with a reputable builder. Went to the dyno session when it was new. 30 minutes at a constant speed to break in cam bearings, oil change, then full throttle, full rpm on a dyno to tune it for power. Makes a guy cringe a little but that motor was hella strong and ran like a top for a long time. Driving it gently might make you feel better but it is unlikely to make a tangible difference in actual longevity.
 

Raz65

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When it shows up it will just get driven normally from day one. So many theories, so many misconceptions. I think that it is total luck of the draw to get a bad one and doesn't have anything to do with how you "break it in". Unless you drive it off the lot and into competition, it isn't really going to matter. I remember having a high performance engine built for my old Buick, spent a lot of money on it with a reputable builder. Went to the dyno session when it was new. 30 minutes at a constant speed to break in cam bearings, oil change, then full throttle, full rpm on a dyno to tune it for power. Makes a guy cringe a little but that motor was hella strong and ran like a top for a long time. Driving it gently might make you feel better but it is unlikely to make a tangible difference in actual longevity.
Bang on.
 
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nU7OuxIx

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I'm getting the feeling that there really is no hard mileage when the engine/vehicle is fully broken in. The best number I got was from the manual saying 300 miles. To me, this seems low but what do I know.

And I agree with the others about you can baby it and have engine issues later, or drive it hard and have engine issues later. So maybe in the end, it's all out the window and anybody's guess.
 

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In regards to the engine- Rings-wise.... mostly the first time it’s started nowadays with the cylinder wall finishes. Valvetrain would be the next hot spot really but the multi valve heads with small valves and resulting low weight don’t need much valve spring pressure to control and the movement across the stem is small so not much friction/heat there either outside of the exhaust valve.

I’d just follow the manual as it wouldn’t take something long to detonate if something was “wrong”. That will allow the engine and the rest of the drivetrain time and heat cycles. There’s the outliers but there’s no sense stressing over the upredictable.
 

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i broke mine in by driving 275 miles home from the dealer. 55-85 every few miles change the rpm/speed. All my work trucks get put into daily service the day we bring them in. that could mean putting a 1400 lb pump inthe back of the half ton trucks. all our trucks are serviced in house regularly per the manuals. Most of your trucks make 300K or more miles without any major issues. I believe that with how good tolerances have become with new cnc machining that break in is a thing of the past. I also agree though that new vehicles should not be raced around at max rpm in the first few hundred miles either. Just go about your normal driving habits and you should be fine
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