How many miles would you run an M42 after it was beeing rebuild, until reving it

[M3Philipp]

I wonder how many miles or kilometers you would drive the M42B18 engine, after it was completly rebuild.
Meaning new bored, honed, new pistons...
How long do I have to drive it, until I can rev it to the maximum, meaning around 6500RPM?
I have 2000 kilometers on the clock now.
An oil change including oil filter was done at 1100 kilometers.
Can I push the engine to the limit now, or do I still need to drive "normal"?

[nrubenstein]

BMW's engine break in is 1,200 miles. I don't see why ou would need to go longer.

[M3Philipp]

Does this go for all BMW engines, new and old ones, or was this specific for E30 engines back then?

[nrubenstein]

Does this go for all BMW engines, new and old ones, or was this specific for E30 engines back then?

BMW has specified 1,200 miles on every one that I've seen (which is a lot).

Anyway, the long run in is crap. I just wasn't going to get into that since you've already done it.

[Massimo]

Most cars are usually around the 1000km mark I would change your oil again, and go for your life.

[bmwman91]

What kind of oil were you running during the break-in period?

[TobyB]

The sticker still on the inside of my windshield says 1200 miles.

Now get on it!

That said, I do watch revs right at first, but also use full throttle as soon as I possibly
can- I've had good luck with ring seating that way...

Right at first being maybe the first 10 miles, btw...

t

[M3Philipp]

I ran 5w40 full synth. oil within the first 1000km.
After the first oil and filter change, I did put in a 5w40 full synth. oil again.

[Dj Buttchug]

i wouldnt run full synthetic on a brand new engine. run conventional for initial break in. it aids in cylinder lap ect.

[nando]

BMW's engine break in is 1,200 miles. I don't see why ou would need to go longer.

that's way too long if you know what you're doing.

100 miles is enough to seat the rings.

[nrubenstein]

that's way too long if you know what you're doing.

100 miles is enough to seat the rings.

As I said earlier, I wasn't going to get into why that's unnecessary when he's done 2,000km.

[nando]

sure, but others may be reading this thread too, and thinking they need to drive like a grandma for 1200km.

as you probably know that's a good way to glaze the rings over.. :)

[bmwman91]

I had a Metric Mechanic M42 built and here's the procedure they recommend:
- Use 10W-40 mineral oil (NOT synthetic under any circumstances)
- Get the engine running and drive it a couple of miles to verify function.
- Find a straight, empty road.
- Floor it from 2000RPM - 4000RPM.
- Let off the gas and let it slow itself back down to 2000RPM.
- Floor it from 2000RPM to 4100RPM.
- Repeat in 100RPM increments up to 4500RPM.
- Drive a few miles under light throttle.
- Repeat the cycling process again, revving to 4500RPM.
- Repeat in 100RPM increments up to 5000RPM.
- Drive 50-60 miles, never revving over 5000RPM, with a mix of throttle and engine speeds.
- Change the oil & filter using more 10W-40 mineral oil (NOT synthetic).
- Drive 500-1000 miles on this oil, never going above (max RPM - 1000). I just continued to keep it under 5000RPM.
- Change the oil & filter using high quality 15W-50 synthetic oil (Mobil 1).
- Rev the dog shit out of it and have fun.

It is a little late for the OP, but this is just for reference for anyone else wondering.

[M3Philipp]

I dont know what to think of all this, because everyone tells something different.
Starting about oil that is best on an M42.
Ok, I heard it all, from 0w40 to 20w50, or maybe just put ATF in?
Now on engine break.
Here it seems the same.
Some say, dont go higher than 4000RPM before you have reached 1200 miles, never.
Then, I heard people saying, push it to the limit almost, after a few miles.

Seriously. :loco:
Now I can choose which person I want to belive.

[nando]

ATF in an engine? no way.