Charles is right,..it is hard to say in precise terms but I've simply relied on long-term experience and what I've observed doing 911's exclusively over the past 30+ years.

Parts that lasted almost forever like cams (barring a lubrication or contamination-based failure), rocker arms, (not bushings), and to a lesser degree, rings; now wear at greater rates with the current crop of normal engine oils and thats what prompted my original post on Rennlist about this subject.

Long before Mobil 1, I used Kendall GT-1 (20w-50) in all race & street engines and I never wore out a pair of cams or rocker arms even using very stiff valve springs with high seat pressures. Pistons, rings, pins & oil pumps all looked excellent even after extended operation well above 7000 RPM under grueling conditions. High-end synthetics did an even better job until the reduction of ZDDP.

Just one man's opinion of course so the normal disclaimer; "YMMV" applies here. :) :)

If the GM additive won't do much for raising the ZnDDP (Zinc diethyl dithiophosphonate ) concentration what about making my own additives? The O,O'- diethyl dithiophosphonate is availabe. I could just react it with a Zn salt and make the ZnDDP. The structure looks like it would be oleophilic and dissolve. This method would allow you to easily add your own loading.

I suspect the ZDDP wiould kill a cat due to the sulfur content. thiols can easily poison the Pt/Ir/Pd metals that chew up the nasties in exhaust.

thio = sulphur

Jamie:

I think its important to maintain some perspective here.

Many motor oils contained sufficient ZDDP additives for many years that were used in catalyst-equipped cars without killing the cats,...:)

I've seen a LOT of 911's since 1978 and I have only replaced 2 cats over this time period and that was due to excessively rich fuel mixtures (bad chips).

Current EPA regulations require lifetime longevity of the cats so these additives have been removed-reduced for compliance. Personally speaking, I'd rather buy a cat or two over 100K-150K miles than a pair of cams, rocker arms/shafts and the labor to install them. :)

Cat technology has changed over the years too. IIRC, the pores are now more numerous & smaller...

So, add a bottle of STP red bottle to my 8.5 quarts of Mobil 1?????
Yeah, I'll confess, I'm looking for a simple answer to a complicated question.

If you're using mobil 1, you don't need to add anything, that's the point :-)

http://forums.hybridz.org/showthread.php?t=100635

This is from a V-8 chevy forum where guys discuss
wiping out their cam lobes on break-in. This link (if it works) shows how often it happens, particularly the BBC 454" motors.
.....FWIW, they suggest that EOS is excellent for BREAK-In but that it is or can be a contributor to clogging an oil filter if left in all the time, as suggested here. Hmmmm....

One specific paragraph from the link :

"BTW ADD E.O.S. to the oil and MOLY break-in lube to the cam before starting the engine and prefill the filter and pre-prime the oil system before starting the engine.
I normally pour it in just before starting the engines cam break in,procedure. because I want to make sure that nothing in the oil/E.O.S. mix can settle out from sitting over a long period of time. Now if your running a flat tappet cam you should have also used a moly cam lube on the lobes and be using a mineral base oil for the break-in procedure, and youll need to do an oil and filter change after about the first 3-4 hours running time to remove that moly cam lube from the engine after its served its purpose of protecting the cams lobes and lifters at start up, AND AS THE LOBES/LIFTERS LAPPED IN. MOSTLY to prevent that moly grease and E.O.S from potentially partially clogging the filter after that mix cools down, but also because both those lubes might leave deposits in the combustion chamber ,over time that might aggravate detonation.
even G.M. suggests that E.O.S. is not a great long term oil suppliment, and that its main function is to add extra oil film strength durring new engine break in."

An amusing story about 3 Cams - wiped out: :(
"I have a 454 that ate 3 cams during break-in so I ended up installing a roller cam to fix that. But, I think the problem was rooted in large main and rod clearances. It seems the two machince shops I had used to rebuild the engine both wanted to set the BBC clearances up like a SBC. And after doing a little research, I found that the BBC needs to be set up much tighter than a SBC."

_____________

'82 Targa - sold
'80 928

Thanks! Then it's biz as usual for me...

The purpose of my whole exercise of testing various oils was to see what makes them differ, and which oils still had decent ZDDP, and which ones didn't. For most of us, it should be business as usual, just like you said.

Charles and all,

I enjoyed your link on oils. I reviewed the data, and the oils that particularly pertain to me, with their respective P and ZN values (ppm) are as follows. I have a 93 993 C4S and an 81 911 SC.

Valvoline VR1 20/50 1085 1293
Castrol GTX 20/50 1157 1422 (what's in my SC now)
Mobil 1 SuperSyn 15/50 1342 1390 (what I will put in my 993)
Mobil 1 ExtendPerf 15/50 1385 1428
Castrol GTX HighMile 20/50 1248 1382

I was thinking of changing to Valvoline VR1 for my SC after I had read Steve's comments, but are the absolute P and Zn numbers what protects the cams, etc from the increased wear you all have been talking about?

The numbers alone make me want to consider putting Mobil 1 SuperSyn or Castrol GTX High Mileage into the SC. I just bought the SC and changed the oil when I got it to Castrol GTX. Steve mentioned to me he has seen some bad things with Castol.

Right now the 993 has Mobil 1 0W40 in it. I plan to change it with the 15W50. (Steve's strong recommendation)

What do you all think?

Thanks,

James:

I think using Mobil 1 15w-50 will make your 993 very happy,...:) :)

Steve,

You and I need real jobs. We enjoy this oil stuff too much!http://www.pelicanparts.com/support/smileys/wat1.gif

ROFL,..I have one but the pay & benefits aren't competitive anymore,...:)

From what I am told, VR-1 is a great oil with excellent shear stability, which is an adequate trade-off for it's lower (but adequate) ZDDP levels.

I too am going to start using Castrol GTX 20w50 High Mileage in place of the normal GTX 20w50 because it would appear to be the same thing, but better. The one complaint I have seen of GTX is that it looses viscosity, but it looks like that it starts life already lower than the specified 20w50, which can't help things and may indeed have thrown off sample results from used oils to begin with. The high mileage was spot on for viscosity.

Mobil 1 pretty much stands on it's own. I use it and will keep using it. I'm waiting to get back test results on the 0w40 euro to see what the difference is between the 15w50, if any, when it comes to what they put in it.

I question the statistical significance of the differences between the "standard" Castrol GTX 20W50 and the High Mileage version P and Zn assays. The differences just barely pass the square root of N "rule of thumb" for being meaningful. How many samples from different lots were run?

I'm pretty much considering both the Castrol GTX normal and high mileage to statistically be the same. There were some differences not noted here, but on the full analysis.

Since I was funding this myself with no additional assistance, I only did one sample of each oil unfortuneately. Sorry!

It is pretty good stuff from what I've observed inside different engines and if a fellow wanted a bit more ZDDP (in the case of racing valve springs), it cannot hurt to add a little bit of GM's EOS product to that. :)

Interesting discussion. The thrify guy inside me has a question for consideration. Valvoline VR-1 has about 1000 ppm Zn and P in their oil (http://www.valvoline.com/products/VR-1%20Racing%20Motor%20Oil.pdf). If I go to their web site (http://www.valvoline.com/products/All-Climate.pdf), I see that the All-Climate oil has about 800 ppm of Zn and P. If I add EOS to this, I presume I can riase the levels of Zn and P to similar levels. since I can get All climate for less than $1/qt vs $2+/qt for VR-1, even if I need to add a full bottle of EOS (about $10/bottle) each oil change, I am money ahead and still get the same protection.

Any thoughts?

Not exactly. Base stocks are formulated differently. I'd choose a good oil to start with and only add EOS if necessary. Don't cheap out on oil, it's an investment.