[So.Cal.Super]

Ahh The great oil debate, well here are my 2 cents to add.

First let’s look at Synthetic vs. Dino oil. Synthetic oil is artificially synthesized. Think of it on a molecular level like this. You take a work bench and dump a bag of dimes out, all the dimes are the same size, even and uniformed (I’m not using a micrometer for this debate)
They transfer heat better do to this and provide uniformed lubrication.

Now let’s look at Dino oil or Conventional, Add quarters, pennies, half dollars, dollars, those gold dollars, etc. Now we have oil on a molecular level that even after refined has a whole bunch of different sizes. What this does is transfer heat less efficient and the larger molecules will clump together and allow less seepage / leaking because it provides less gaps for the smaller molecules to pass by.

How I experienced this first hand,
I changed the rear end oil in my 72 and went to a full synthetic, two days later the axel seals were leaking. I drained the oil, refilled with conventional and the leaking stopped. I was able to go almost another 2 years before they started leaking and needed to be replaced.

The saying goes if it leaks with synthetic, if will eventually leak with conventional.

So if you already have an oil burning, seeping, leaking machine. It is not recommended to switch.

As far as the Zinc debate goes.
Zinc has been drastically cut down or almost eliminated from today’s conventional oils due to catalytic converter failure. I would like to know what the conventional oil of the 60’s levels was. For this I have researched and can’t seem to find the Data any more the Hearsay.

Here are some examples of what I have found about Zinc in some of the oils out there.

Rotella T-1 Currently 700 ppm (parts per million) Per Shell it was recently reformulated,
It used to be 1200 ppm.

Castrol won’t release the information on its GTX or GTX High mileage for proprietary reasons except to say it has lower quantities of zinc. They will say their syntec 20w-50 is 1200 ppm and is recommended for flat tappet cams

Mobil 1 10w 30 has a rate of 800 ppm and this oil is used in many cars with catalytic converters with no problem.

Mobil 15-50 has 1200 ppm; this oil seems to be recommended on a lot of exotic sports cars

Valvoline VR1 Racing oil is the highest off the shelf oil I have found and at 1400 ppm it is not recommended for use in vehicles with catalytic converters.

I will add that the Lucas oil engine break in additive when mixed with 4.5 quarts (per manufacture) will give you 5000 ppm zinc.

This still doesn’t end the debate on which oil is better. Everyone will make their choice for their own reasons I just wanted to add what I have found out over the years and am sure will continue to learn as this is debated probably way past my lifetime.