We use Amsoil synthetic lubricants and Engine Oil
in all the Vehicles We own,and will be firing up
rebuilt 440 in our '67 GTX in the near future-
question is :should We use synthetic initially,or
break in with petroleum base oil,then switch to
synthetics later? I know many European Cars and
some US made Cars come from the Factory with
synthetics in Them,with stickers and info in
owners manuals encouraging continued use of synthetics,but did They use synthetics at initial
start up ?? pros and cons,please..
\ Eric @ Rickety Enterprises...

Conventional oil with the break in oil recommended by the cam maker. Then you can switch to synthetic after a few thousand miles.

I agree, you need to let the rings seat. Synthetic oil won't let that happen.

go with a conventional oil with a high zinc content for break-in and you can switch to Synthetic as per the previous response.

I agree. I have read and read and asked and asked on this very question, and have always been told to go with petroleum based at break in so that the rings seat properly.And as mentioned, if it isn't a roller cam, high zinc content is protective of the camshaft.

don't use synth on break-in.

Read a story somewhere about a guy that used 0W synth during the wintertime for car storage purposes for low-viscosity benefits. Even though the engine was only started and idled durig the winter, it suffered lobe failure on the flat-tappet cam.

Another for conventional. When you do switch, make sure the syn has plenty of zinc. I use Redline's 5W40.

I USE STANDARD OIL WITH BREAKIN ADDIDIVE

I have never read anyone ever recommending synthetic for a break-in on a new build for one of our old motors. For the realitively short break-in time, do you want to go with what is proven or try and blaze a new trail? Most of us don't want to take any chances at that stage.

Good read - Engine break in

I used Mobile 1 full synthetic on my motor with a Lucas oil zinc additive.. Have done this with the past 6 motors.. I have not had one issue doing this...

To each his own I guess but until it does hurt me I will keep using this method.

Yes many new vehicles come factory fill with synthetic. Other than personal opinion and hearsay, have yet to see any quantitative evidence that would indicate it’s catastrophic to brake-in with synthetic motor oil. The base oil is just a carrier regardless of type. As long as the lubricant has the proper balance of anti-wear additives properly blended in, either type will do the job.

That said, the brake-in oil is generally in for such a short time before drained. This is a costly waste with synthetic.

I’d use a properly blended engine break-in lubricant like Brad Penn SAE-30 before making the switch to synthetic.

And you could play the part of lubrication engineer and blend your own with aftermarket oil additives, but why do such a thing when you can just buy the properly blended and balanced lube designed for the job?

i need to clairify my previous post
i use a simple oil 10 w 30 with the lucus
engine breakin additive, ,
after breakin is done then switch to sythetic
5 w 30 mobil
we do not have any poblems ,
but we also need to say that only flat tappets
neeed this zinc to survive
roller dont need ,,nor warrent such additive!
nor does hyd lifted cams

Best flat-tappet break-in?

My opinion, dont use synthetic's, dont use additives.

Get some Brad Penn 30wt break-in oil.