I don't mean to beat a dead horse, but this question keeps coming up. How much zinc is necessary for a Y-block that has been properly broken in? I seem to recall Ted saying that he uses Valvoline 10w40 Conventional Daily Protection, which, according to Valvoline, has 760 ppm. Others seem to think the oil should contain 1200 ppm. I don't see how you can prove with 100% certainty that you wiped the cam because your oil didn't contain enough zinc. 

I have 38,000 miles on my 312 using Valvoline Conventional 10W30 with no problems

SE Wis

Just keep in mind that too much zinc (also referred to as zinc overloading) can also speed up camshaft wear.  My thought process on the zinc/phosphorus amount is if 1200ppm is good for 5000-6000 mile oil change intervals, then reducing the ZDDP levels in half also reduces the oil change interval to 2500-3000 miles.  Zero issues on my end with the 700-800ppm Zinc/Phosphorus amounts in the oil but I adhere to the 3000 mile max oil change intervals.

Here's the link to a previous thread on this site showing a camshaft that was run with too much zinc in the oil.
http://forums.y-blocksforever.com/FindPost162680.aspx

Lorena, Texas (South of Waco)

There is another factor that probably should be considered about oil change intervals.

Conventional multi-grade oils always use viscosity improvers to produce the desired operating temp (100C)  viscosity (also referred to as the  SAE weight)

For example, any NON-synthetic 10W30 is actually an SAE 10W oil that has sufficient vi improver to raise the weight to operate as a 30wt oil @ 100C 

So a 5W30 is 5W, 10W-30 is 10W and so on.  the larger the "spread" between the lower number loosely means more vi improver is needed to get the oil to the higher number.

The "wear" or "stay-in-grade" (@100C) capability of the oil is directly related to oil change interval because the vi improvers  "wear-out",  so much so that the longer the oil is used, the lower the viscosity will go until the oil becomes very thin approaching it's "room temp" or winter temp viscosity.  Used oil analysis will verify this. 

If you want to know more about SAE "Grade" and it's relationship to viscosity see ---->  https://wiki.anton-paar.com/en/sae-viscosity-grades/

The ability of the oil to "hold" contaminants in suspension is also affected based on the "detergent"  performance of the oil, that will become less effective as the detergents become overwhelmed.  All of us usually change oil long before this happens. Diesel engine oils are a great example of this with it's ability to "hold" soot particles (small enough to pass through filters) in suspension. 

Used oil analysis will also show soot levels.  Diesel fleet operators do used oil analysis to determine when to change oil in their vehicles.  It's worth it for deciding when to change oil for hundreds of vehicles.  Not sure if it's worth it for me.  A couple of oil changes per year is not all that expensive.

Synthetic oils boast longer drain intervals partly because they do a MUCH better job staying in "grade" and that's because they're "designed" to be a straight-weight oil that simply speaking, does not get  (as) thick at room or even winter temps.

So the 0W/5W/10W/20W-----30/40/50 synthetic is actually an SAE  30/40/50 weight oil (with NO vi improvers needed) and stays in grade for MUCH longer than it's conventional oil counterpart.

Those synthetics "perform" like the lower weight oils at the lower temps But are actually the higher weight oil at "running" temps  where you actually want to use them.

The ZDDP levels are another issue.  They are added to "regular" and synthetic oil as part of the additive packages.....     But I cannot add anything to what's already been (correctly) said above!


Camshaft wear is a ZDDP issue that I am sure Ted has extensive experience dealing with!   And if I am not mistaken, the most wear occurs when it's not lubricated properly with the "right stuff" at installation and initial "break-in"

Cheers,

Rick







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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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Too much and not enough along with frequency of changes can really mess with one’s mind. I have been using Lucas Hot Rod 10w-30 for almost 10 years and over 12,000 miles. My frequency is once a year. Their zinc spec sheet is 2100 ppm for the Hot Rod and 861 ppm for their standard oils.
Their synthetics vary and some are much higher especially marine and racing oils. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I've been running the Amsoil ZRod for 3 years now.  No odometer but I'd be very surprised if it hits 3,000 miles in a year.