Why? (synthetic oil bad for breaking in engine?)

[Crusty]

Why do people consider synthetic oil bad for breaking in an engine? I've heard many arguments over the years, but none of them make a lot of sense to me. Supposedly, synthetic oil is "too slippery" and won't allow the rings to seat properly. Is there any evidence that can confirm or deny that? Or is it in the same category as Slick 50 is so slippery, it will cause your roller bearings to slide and not roll and that will cause flat spotting.

Erik Buell was putting synthetic oil in the engines of EBR 1190s and I know a few people who ride them and none have experienced either poor piston ring sealing or flat spotted bearings.

I'm breaking in the engine gone through by Dark Horse. When I picked it up, Andrew, the CS Rep, instructed me to break it in using non-synthetic oil.

I'm doing that, but it has me wondering why.

Would it really adversely affect my engine if I were using Syn 3, Amsoil, or Mobil 1 instead of Plain Ol' 20W-50 liquified dinosaurs?

[84rzv500r]

my experience in 50 years of building and racing is that ring seating is less dependent on oil type and more dependent on bore finish and ring material, proper end gap and thermal cycles (new and in use)... that said if engines have new sliding thingies like flat tappets then i prefer dino oil with some zinc for the first few thermal cycles till they get to know each other... after that synthetic... for rollie thingy motors, synthetic out of the gate not an issue. also for daily runners... for occasional use engines dino or semi syn...

[Hippysmack]

You only get 1 shot at a proper break in.
Per Aaron w/Hammer, some engines aren't ever fully broke in no matter how high the miles.
The theory is that dino oil WILL ALLOW more metal scrappage than synth.
The rings NEED to be able to cut the cylinders into their own shape to achieve proper seal.
Break in is considered the final machining process.
MAKE SURE to change the oil/filter after break in.

The reason there is no pliable data is that when an engine takes a dump, it COULD have been from a number of reasons.
From the forum, sometimes an affect and cause gets very hazy.
If you spin a bearing, was it the oil? was it your heavy hand? was it poor installation? was it? was it? was it?
So using dino is an extra finger to cross in a way.
For those who break in on synth that have good results, they'll scoff at dino break in.
For those that break in on dino with no problems, they'll be happy they did.
And as always, when things go wrong and the cause cannot be fingered, the wonder may always be there.
But each scenario only happens once. The rest is up to the owner/builder to answer later.

[rokytnji]

Dino is cheaper than synth. I am throwing it out anyways sooner than later.

But I am simple minded.

[Crusty]

I believe in early and often oil changes when I'm breaking in a new engine. I change the oil at 50, 250, 500, 1,000 and 2,000 miles before going to longer intervals. Rokytnji makes sense about the money saved by using Dino over synth.

But I still wonder if there any evidence to support either argument. Hippysmack also makes a lot of sense.

Then again the theory of Phlogiston made sense until Lavoisier disproved it.

I will follow Dark Horse's recommendation with the exception that I'll change the oil a bit more often for a while. Still; some objective proof either way would be nice.

[Hippysmack]

Yes.
Above all else, follow your builder/supplier recommendations (if you value a warranty).

[Steve9]

Some people use high zinc oil specified as break-in oil. Makes sense to me

I don't think syn would hurt, main thing is dump it soon, as the break in process puts lots of little "broke" particles in the oil

This is just what I think, not a highly experienced opinion.

[bustert]

corvette come factory filled with syn.
mr. 500r nailed it!
hummmm, ring cut to shape of cly?? rings are dynamic, aka, they move around.
i picked up a SWEET deal on a 1974 fx since the guy who rebuilt the top end install the rings upside down and it burned more oil that before, he got scared and bought a new machine.
on ole trick when using chrome rings was to use BON AMI mix in the oil, but get the RIGHT one as the made two, you want the one that says WILL NOT SCRATCH!!!
but then again, goes back to mr. 500r, proper cut.

[Andy56]

A guy I worked with years ago had a Yamaha R1. The manual instructed to use mineral oil for break in and not exceed a certain rpm even when broken in until filled with synthetic oil.

BMW for their M5 used to use mineral oil for the first part of break-in.

My first new BMW came with synthetic oil and it used quite a lot of it for the first 3 to 4,000 miles. Then it didn't use any during the rest of the time I had it covering 122,000 miles.

On a site about karts the guy talks about seating rings in maybe an hour or so using mineral oil and then switching to synthetic for the first race.

[Whitewalls]

" Break-in Oil vs. Regular Motor Oil
What is break-in oil? It’s typically conventional-based lubricants containing zinc/phosphorus (ZDDP) and moly anti-wear compounds. ZDDP forms a polar attraction to surfaces in the engine and creates a sacrificial layer. This prevents metal-to-metal contact in areas where a full-fluid oil film cannot exist. For instance, between cam lobes and lifters.
Molybdenum disulfide is a sulfate-based additive that protects against corrosion and oxidation while also reducing friction. We should note that it’s important that engine break-in oil contains an aggressive detergent/dispersant package to trap contaminants and metal particles, keeping them away from engine parts."