Kerrmudgeon

If you want to use synthetic oil for a new build, can you add a zinc compound for use with flat tappet motors?? I like the cleaner running synthetics but I don't want to damage anything. Maybe break in with regular break-in oil and switch??? Thanks in advance.

Procrastination Racing

Back when all we had were the Third Generation Small blocks (1986 - 1996) and older and synthetic was showing up, I think the recommendation was to break in on regular oil, run the first 1000 miles, then switch, although I think the Corvettes left full of Mobil 1 from the start.

Of course, some of that was different types of rings and flat tappet cams which needed to seat in the engine (non-Corvette). Most of today's engines are roller lifters and rings are different and they leave the factory full of synthetic oil.

DansYellow66

I would definately start and break in with a high ZDDP oil like Brad Penn or something and run if for a couple thousand miles. Then maybe Mobile 1. I used to run Mobile 1 in my old cars and suffered no damage that I'm aware of, but later switched to Diesel oil after understanding all the changes the newer oils were incorporating. But breaking in a new, older style motor on synthetic is not a good approach in my opinion.

Kerrmudgeon

That was the plan... to break it in with Brad Penn break in oil, then switch to a synthetic after a 1000 miles or so. But should an additive be used with the synthetic on a regular basis?

Lou64

I use Mobil 1 15w-50 synthetic. It is on the list of acceptable oils and should work great for a new build, but I am noticing a lot of leaks on my old engine at the gaskets.

DansYellow66

A good question. By it's nature synthetic oil would seem a little slippier than conventional oil which should help with flat tappet cams - but oil film science and mechanics to prevent galling are not nearly that simple as evidenced by the ZDDP issue. Maybe someone has a definative answer but if I were still running synthetic in my old cars I would probably put in a half bottle at oil changes just for some addiitonal peace of mind.

Kerrmudgeon

That sounds like what I had in mind. I was only concerned about possible interaction between the two. And knowledge out there??? :

Dan Hampton

Is there some particular reason that you need to run synthetic oil?

jdk971

i have always been told to use reg oil with the zinc to set the rings. then if you must change
to synthetic later, they mix fine. check but i think you want non detergent also for these old
engines for break end. jim

Kerrmudgeon

Just because it has no ash in it to burn and turn black, less deposits, longer 100% performance, better lubricity, stuff like that.

joebobbilly

Rings wont seat using synthetic oil = myth.

Dicecal

I just use this, all the Zinc you need.
https://www.amsoil.com/storefront/zrt.aspx

Kerrmudgeon

thanks, I just checked and there is a distributor just down the road from my, just a name, not a business, so we'll see......

Frankie the Fink

Been using this for 5 years with a Duntov 097 cam/solid lifters in my '61. NAPA sells it and it's formulated specifically for older, flat tappet cars. If its a SBC then put the oil adapter on it and run a NAPA-1794 2 QT truck oil filter and "....keep on truckin".

Synthetic oil causing leaks is a total myth...it may however seep through some areas which your old oil didn't and those should be fixed anyway. Should NOT be a problem on a new build.

DansYellow66

Frankie - are you saying Mobile 1 15W-50 is formulated for older motors? Never heard that before. And why NAPA - I can buy Mobile 1 anywhere these days? Are you finding a unique Mobile 1 product that is specifically advertised or labeled for older cars? If so, I would be interested in knowing what the container says on it as far as the oil API rating, etc.

I don't know about more leaks with synthetic. I think it probably does tend to weep a little more - probably due to some of the older gasket compositions and gasket uses. One interesting thing I noticed several years ago when I changed to synthetic transmission lube in my Muncie (I'm intending to switch back to dino lube) is that after a few months the entire aluminum case took on a sheen like it had been wiped down with oil. Not gasket leaks, more like the aluminum became impregnated with it. I can't feel it and it's not oily to the touch - just has this shiny sheen to it. Curious if anyone else has noticed something like this?

Dan

Frankie the Fink

Read the ZDDP levels and description. Zoom in - it's a bit of an eye test. 15W-50W is a tad harder to find than the more run-of-the-mill weights so NAPA was just a suggestion -- I've always found it there...if you can get it at some other FLAPS or Wally Mart good on ya.

Your transmission is shinier with synthetic because it's happier. You will also find your teeth are whiter and your testosterone level is increased.

DansYellow66

Damn - at my age that may be a real bargain.

C66 Racing

For those considering the above, if you buy via this link the sale will be credited to a random dealer in your area - drop me a line and I'll save you money and the forum will benefit.

More than happy to get AMSOIL products for forum members at dealer wholesale pricing, about 25% below retail, via the AMSOIL Preferred Customer Program. Drop me a PM if interested.


For the OP, my opinion is that while ZDDP is important, how it is blended in is equally important. More zinc is not necessarily better. Though a little dated now, this AMSOIL commissioned study of motorcycle oil showed that the oil's with the most zinc did not perform the best in wear tests (pages 12-14):
AMSOIL Motorcycle Oil “White Paper” (1 MB pdf file)

JohnZ

Forget all the exotic "boutique" and synthetic oils - just use a CJ-4 oil (any brand, 10W30 or 15W40), and don't worry about it; any CJ-4 oil has all the Zinc/Phos you need to protect your flat-tappet valvetrain.

ndotti

Got my '67 small block back from a complete engine rebuild recently. I asked about oil and the use of a synthetic, assuming it was "better." I was told the older style gaskets, etc. are really designed for fossil oil and the synthetics, while great, are too slipery and to expect leaks. This seems to be consistent with what I read above from a few people. I'm using Valvoline VR1 (20W-50) "racling oil," which has the high zinc content; no need for addatives. Bought a case from a local NAPA dealer and it cost just about the same as "normal" oil.