FYI - Engine Break-in Recommendations with Science Behind the Why

[Lion77]

Understanding Engine Break In | Dos and Don'ts

Great video that provides some insight into the "why" which explains the recommendations in Ford's owner's manual. My Mazda 3 and CX-9 owner's manuals also mirrored the recommendations in Ford's for my 11/24 RR.

I followed the manual's instructions as much as possible for the 3 and RR, but my wife's CX-9 already had 2,300 miles on it when I got it, so not much choice on that one other than hope the dealer (was a demo car, 9k below sticker) didn't do anything outside of those recommendations.

2024 Ranger Owner's Manual

As per the service manual linked above, the only information provided in the service manual which has been posted in other threads is the following:

"Breaking-In

You need to break in new tires for approximately 300 mi (480 km). During this time, your vehicle may exhibit some unusual driving characteristics.

Avoid driving too fast during the first 1,000 mi (1,600 km). Vary your speed frequently and change up through the gears early. Do not labor the engine.

Do not tow during the first 1,000 mi (1,600 km)."

Most of us generally try to follow the recommendations, but there is often much debate as to the "why". I think hearing from engine development engineers provides some significant credibility behind the "why" and that's the purpose of this post, which is knowledge transfer (educational).

Summary of Do's and Don'ts During Break-in

1. Do not tow to avoid sustained high loads at constant RPM.

2. Try to vary the engine RPM across the range mid-range frequently during the breaking process (i.e., back country roads with periodic stop signs / stop lights, merging onto highways at moderate throttle, down-shifting frequently on the highway etc.).

3. Avoid any sustained high RPM / Wide Open Throttle operation (highway pulls, drag racing etc.) to avoid excessive thermal loading during break-in.

4. Do not run the engine at very low rpm at high loads (lugging) due to decreased oil film strength at lower RPMs, which can adversely affect break-in by causing localized heating on the bearing surfaces during mixed mode and boundary layer lubrication regimes where a partial oil film forms (rotational velocity, surface area and temperature dependent).

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[Lion77]

I wanted to add that "changing up through the gears early" means do not rev it out too far as up shifting implies the next taller gear ratio. Many people suggest avoiding going over 4k rpm for the first 500 miles which I agree with and believe fits the recommendations very well, then maybe up to 5k periodically in the last 500 miles until you hit that 1k break in.

I've done this very same thing, just enough throttle (not in boost) to get it in those ranges as frequently as I can. The goal is varying RPMs at lighter loads where heat and pressure are moderate during wear in.

I did a mixture of highway driving, back country roads and around town. I personally did use cruise control on the highways, but I used the paddle shifters to downshift through the gears ever few minutes and then let it hang at 4k for the 3 seconds until the PCM starts up-shifting on its own. I also took the opportunity to pass slower vehicles with just enough throttle to get it to downshift a few gears into the 3k-4k range.

There are different methods, some people don't use cruise and just vary speed slightly with throttle in the same gear, I tend to like cruise to keep me from speeding accidentally on public roads and using the paddle shifter method.

I think they all accomplish the same thing and adhere to the intent of the recommendations.

 

[stemplar]

If possible, the title of this thread should be changed to reflect that it's about engine BREAK-IN and not engine BRAKING

 

[Lion77]

Might need a mod to change it, I don't see an option to change the threat title.

 

[Lion77]

fixed the title, found it in a sub-panel.

 

[KingsRanger931]

when should the first oil change be?

 

[Lion77]

Most people change it around 1k - 1.5k miles primarily to get rid of silicone in the oil from manufacturing. I don't personally buy the "metal particles in the oil" as being an issue because that means your filter isn't filtering...why would the filter not be filtering larger metal filings when it should be handling particulates well into the low micron range?

In reality it's the chemical byproducts of mfg. that are of some concern as they can interfere with the oil's performance (particularly silicone), so it is believed (I have not seen any evidence of this on a testing basis, but some powertrain engineers have made such statements, so I think there is some merit to it).

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