The title tells everything: what oil should I use to fire up a freshly rebuilt engine?

On some sites I saw to run full organic oil as it is required in the first few hundred miles. Is that true or just some kind of urban legend?

 

Not urban legend - synthetic oil is too 'fine' and won't allow the rings to break-in. That's the whole point of synthetic, it can get to places that dino oil can't, which is part of why it cleans better.

It's a SBC right? I'd say 10W-30, 5W-30 wouldn't hurt though.

 

Might want to tell the manufacturers about that, they're using synthetic for the factory fill on all their new engines.

 

Seems like this is going to be the same that I read at other places as well.

 

But are newly built 2010/11 motors he same as a rebuilt engine from who knows how long ago?

Two very different things.

 

Well it's not like you'll hurt anything by not breaking it in with synthetic. You're also not going to hurt anything by breaking it in with synthetic, too. Either way you can't lose.

 

Yes, they are. Cast iron cylinder walls, cast iron rings with or without moly facing, aluminum pistons, steel valvetrain components... that kind of engine technology hasn't changed in a looooooooooooong time.

 

Then please explain to me why everything I have ever read about breaking in motors has explicitly said to use non-synthetic oil.

 

Because you've read rumors and old wive's tales, not facts from people who produce lubricants and build engines.

 

I see no facts here, only what you have said.

EDIT:

What modern companies use synthetic? Because GM paperwork has always said organic oil.

 

GM uses Mobil 1 for the factory fill in the Corvette and Camaro.

 

True i have read companies do break ins on factory motors with synthetics.

For my 2 motors, I used regular conventional 10w-30 for initial break in for first 25-50miles. Changed oil to same stuff for another 25 miles or so when doing hard pulls for break in. 1st gear pulls, lower load, higher rpms. Then moved on to 2-3rd gear heavy load pulls to 90% of max rpm.

After that and likely before 100 miles, i went straight synthetic and proceeded to go racing. Never had a problem.


Now if you have a Flat TAPPET cammed motor, you will need a high zinc oil for lubrication on cam break in. They sell special oils for that as most modern oils now do not have proper lubricants for flat tappet cam break ins.

My motors are hydraulic rollers, so you can just fire up, check for leaks and go drive.

One reason to break in on cheap conventional oil is because its CHEAP and you need to change it out a few times after little mileage on the motor. Dont waste synthetic for that

 

This is what I was going to ask. Is it a flat tappet or roller engine? I have been running Rotella in my flat tappet engines. You will need oil that contains 1200 ppm of zddp if it is a flat tappet engine. Rotella, Delo, and Walmart heavy duty all contain 1200 ppm of zddp. Actually the walmart brand has 1300 ppm.

 

Fortunately it is a roller engine.

 

 

Seems like this is going to be the same that I read at other places as well.

 

Run Mobil 1 then.

 

What my machinist says about synthetic is it doesn't allow the rings to seat properly because it prohibits wear. That's why I run organic oil for the first 1,000 miles. Then switch to Mobil1

 

What brand do you suggest, Ase? Who makes full organic oil?

 

I've heard this also. I've also heard to the contrary. Gets frustrating.

 

Ya know? I guess whatever works for you. I suppose the worst that could happen if you switch to synthetic too soon is excess oil cunsumption. Cylinder finish will have a large effect on this. Having the correct finish for the rings you use is important.

 

I would like to see empirical evidence that synthetic oil is too slippery for break in.

 

This is what Mobil says:

http://www.mobiloil.com/usa-english/...ics/myths.aspx

 

That's pretty much it. With bad surface prep you'll glaze the cylinders no matter what oil you use.

Orr89RocZ has the real reason to break in with conventional oil.

 

I've been running M1 Hi Mileage 5W30 in my 88 LB9 for years. Winter and summer.

Don't use the Fram orange can of death filters. Wix makes a good filter. So does K&N.

And I also recommend going and reading the BITOG forums. More than you ever wanted to know about lubrication.

 

Old thread...do guys listen to their builders suggestions or ask the internet instead?

 

I run Mobil One or Pennzoil Platinum on everything from day 1.