oil
 

I have been using shell rotilla 15 40 I understand there is no more zinc in it. to-day I was in the parts store and STP in the blue label has zinc and ZDDP in it so I'm going to add a can to the shell. Has anyone tried this?. Jack

Re: oil
 

If you think you need zinc, take a look at Valvoline VR1 20W-50 racing oil. Stocked at all parts stores, and not much more expensive that regular oil.

Re: oil
 

Yes, I used the STP for that reason. At that time, it was in a blue bottle.

Re: oil
 

I bought a bunch of "Peak" (the anti-freeze people) oil at Dollar General for $1.85 a quart. I don't know what the zinc content was, but it was marked "Not to be used in vehicles manufactured after 1985".

Re: oil
 

I still run the Rotella T4 15-40 in all my flathead and diesel engines with no worries.

Re: oil
 

Penn Grade is very good, little pricey, but enough zinc.

Re: oil
 

Hi Everyone, Not trying to stir up a hornet's nest, but what makes you want the zinc?

Re: oil
 

Flat Tappets. It's actually a compound called ZDDP, which contains zinc and phosphorus among other components, and is a lubricant for very high pressure contact areas between metals. The cam/tappet contact area is one of those. The zinc content is oils has been slowly reduced until is/almost is non existent in most oils today. EPA restrictions.....

Re: oil
 

All oil still has some (plenty enough for a flathead) zinc in it. Do you think oil in the '30's and '40's had zinc in it?? Nope! I've seen flatheads totally worn out, more smoke coming out of the road draft tube than the exhaust, which was pouring out blue smoke, wrist pins rattling, mains thumping, rear main pouring out oil, and the cams were fine. By the way these poor old clunkers were usually fed re-refined oil (no detergent, no zinc, no nothing).

Re: oil
 

The ZDDP is to make up for not having leaded gas. That's the point. supposedly the lead in the gas helped with tappet wear. Just what I've been told by many old-timers, some of whom were auto engineers for the big three.

Re: oil
 

Don't think so. Lead has to do with valve seats and stems, not the cam to lifter surface.

Re: oil
 

STP is not a lubricant, beware. Adding it makes the oil thicker
but is also diluting the oil.

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Valvoline 10-40 has lots of Zinc in it. Recommended by a noted YBlock engine builder. He uses it in his regular and performance engines.

Re: oil
 

There is so much BS out there about zinc. All oils still have plenty of zinc for our flatheads. Adding it to your oil is a waste of money and in some cases can actually do harm. Forget about it.

Re: oil
 

https://540ratblog.wordpress.com/


Probably more than you ever wanted to know about oil, but this blog is one of the best in my opinion. I used it to help me pick an oil for my old cars. Make sure you scroll down a good ways to find his rankings...

Re: oil
 

I ran synthetic for 8100 miles and when I changed it had an oil analysis done. They said try 9000 next time.

Re: oil
 

It’s been said on here, by someone a lot smarter than me about our beloved Flatheads, just about any oil you buy today is better than what you could buy 70 plus years ago. You can pick your oil by the color on the jug if you want........ Mark

Re: oil
 

Y-blocks are in the OHV category so a little more zinc/phos would be OK for them but flatheads have large flat tappets an low spring pressures so it's not really needed. The API ratings can tell you how much zddp is in there but you have to remember that the older ones like SG are obsolete and not regulated as such. Not all modern motors have roller tappets. Some are still flat tappet and they do fine on the later 800 ppm zddp additives. It's the motors built from around 1958 through 1973 or so or hopped up engines that were high compression and high spring pressure that needed the higher 1200 ppm rated oils. This was the reason for the increase in the first place.

Re: oil
 

Yep

Re: oil
 

On that very good 540Rat blog, Note that Chevron supreme oil has large amounts of ZDDP, and available at my Costco store at about 4 bucks a quart.
I use 5-30 in my flathead. About the best bang for the buck
Seems to work fine
Jim

Re: oil
 

mrtexas was a chemical engineer in the petroleum industry. He would know about the benefits of lead and zinc in oil.
Bruce

Re: oil
 

Mr. Texas, Please review attached oil test results and let us
know what you think of Cummings Blue. G.M.