Classic vs Modern Engine Break-In

[camrydriver111]

I see a lot of topics on engine break in, but not a lot on the differences on classic vs modern cars.

Modern cars are filled with fully formulated synthetic at the factory and driven off the assembly line.

If you do this after rebuilding an old engine, the piston rings won't seal properly, so you need to run a break in oil, or at the very least conventional oil. Synthetic oil is actually too good at preventing wear.

Why are modern cars able to do this, but classic cars can't? Is it the surface finish of the cylinder walls? Is it special materials like Alusil or Nikasil? If break in is the final step of the honing process, do modern engines just have this step already completed? Is it the assembly lube they are using?

Is it actually beneficial to dump the factory fill? If you run the factory fill for the full OCI, maybe the extra metal have an abrasive effect and mimick the effect of break-in oil?

 

[buster]

I'm not sure if there is a difference between breaking in a classic vs modern engine. The first 20-50 miles or so is when rings seat. It doesn't take an enormous amount of pressure to do so either. Varying rpms, generally no higher than 4k, is sufficient enough to break in the engine. You don't want to baby it or WOT to redline either. Basically city type driving is best. Avoid extremes.

Good question about the FF. I know Honda remains pretty adamant about keeping their oil in the engine until the first OCI is down to 15% of the MM. I'm not sure what their reasoning is other than the FF oil does contain a good dose of moly.

 

[kschachn]

I see a lot of topics on engine break in, but not a lot on the differences on classic vs modern cars.

Modern cars are filled with fully formulated synthetic at the factory and driven off the assembly line.

If you do this after rebuilding an old engine, the piston rings won't seal properly, so you need to run a break in oil, or at the very least conventional oil. Synthetic oil is actually too good at preventing wear.

Why are modern cars able to do this, but classic cars can't? Is it the surface finish of the cylinder walls? Is it special materials like Alusil or Nikasil? If break in is the final step of the honing process, do modern engines just have this step already completed? Is it the assembly lube they are using?

Is it actually beneficial to dump the factory fill? If you run the factory fill for the full OCI, maybe the extra metal have an abrasive effect and mimick the effect of break-in oil?

How old? I never had a problem with my 1982 Mazda engine, nor with an early 90s Honda. It sounds like Internet nonsense to me, especially considering the synthetics of today are nearly all Group III which is more or less chemically identical to Group I or Group II base stocks.

And that question about dumping the factory fill early, there are tens if not hundreds of long threads on that topic. In fact there was another one just recently.

 

[BMWTurboDzl]

I see a lot of topics on engine break in, but not a lot on the differences on classic vs modern cars.

Modern cars are filled with fully formulated synthetic at the factory and driven off the assembly line.

If you do this after rebuilding an old engine, the piston rings won't seal properly, so you need to run a break in oil, or at the very least conventional oil. Synthetic oil is actually too good at preventing wear.

Why are modern cars able to do this, but classic cars can't? Is it the surface finish of the cylinder walls? Is it special materials like Alusil or Nikasil? If break in is the final step of the honing process, do modern engines just have this step already completed? Is it the assembly lube they are using?

Is it actually beneficial to dump the factory fill? If you run the factory fill for the full OCI, maybe the extra metal have an abrasive effect and mimick the effect of break-in oil?

My guess.

Greater degree of manufacturing precision,
Roller cams
Changes in metallurgy
Running-in at the factory during assembly.

I haven't seen a UOA which performed a particle count on the number and size of various particles found in a sample to confirm whether the initial wear was abrasive. There's this thinking that high initial wear numbers in a UOA are actually contributing to engine wear.

If you think about it, for the last 20+ years can go for 200k-300k miles with simple oil changes when back in the 1980's people would look to dump their cars at 100k miles because of high oil consumption.

 

[ATex7239]

I'm not sure if there is a difference between breaking in a classic vs modern engine. The first 20-50 miles or so is when rings seat. It doesn't take an enormous amount of pressure to do so either. Varying rpms, generally no higher than 4k, is sufficient enough to break in the engine. You don't want to baby it or WOT to redline either. Basically city type driving is best. Avoid extremes.

Good question about the FF. I know Honda remains pretty adamant about keeping their oil in the engine until the first OCI is down to 15% of the MM. I'm not sure what their reasoning is other than the FF oil does contain a good dose of moly.

Anecdotal: Years ago I was regularly working as a vendor at a major auto manufacturing plant. While working around the facility I noticed that periodically one the vehicles would be taken straight off the line outside for what appeared to be 0-60/60-0 test. WOT from full stop then an immediate hard brake to full stop. I witnessed this event over many months and many vehicles.

I once owned one of the same vehicles made at that specific plant. Never had issues with the engine. And who’s to say mine didn’t have the same thing happen to it. This was one of the contributing factors that made me realize how much I was probably overthinking break in/break in oil changes on modern vehicles. I run the intended interval and just drive like normal from day one.

 

[thastinger]

Classic cars can certainly do this, they are just using the wrong machine shop and piston ring combo.

 

[wpod]

Engines can not help but to break in despite the oil used.

 

[TomYoung]

If you do this after rebuilding an old engine, the piston rings won't seal properly, so you need to run a break in oil, or at the very least conventional oil. Synthetic oil is actually too good at preventing wear.

You are asserting this, or simply stating as though it is accepted, common knowledge. I dispute that and would note that most of the cars on the road and most rebuilds have probably never seen anything other than synthetic oil.

 

[930.engineering]

If you do this after rebuilding an old engine, the piston rings won't seal properly, so you need to run a break in oil, or at the very least conventional oil. Synthetic oil is actually too good at preventing wear.
Why are modern cars able to do this, but classic cars can't? Is it the surface finish of the cylinder walls? ....... If break in is the final step of the honing process, do modern engines just have this step already completed? Is it the assembly lube they are using?

I don't think local machine shops use the same advanced multi-million dollar tech huge factories use.

Is it actually beneficial to dump the factory fill?

We had that discussion a thousand times. I prefer to do it with any car.
.
.

 

[vpr5703]

I've heard that break in differences *CAN* be attributed to the different metallurgies used in the rings and cylinder walls. Older materials might want/need/whatever to be broken in differently (hard break in vs varied running vs light loads, ect....) because the hardness of the rings and cylinder walls change how the rings seat.

I'm not an engine builder or anything, but it makes sense that more modern materials might change the break in process or possibly negate it, depending on how the OEM builds the engines. Dunno for sure, though.