theiceman

Me too

myflat6

Yep, me too

BER

We don't need no stinking' cats! Real 911's don't have cats.

My oil...Joe Gibbs DT50...high in zinc and it eats cats.

BLACK3.2

grgallo

agree cat-less for the old boys, my cat is gone so nothing for my high zinc oil to eat

Bill Verburg

There are multiple good answers to the op 's question but it''s amazing to me the # of ill informed responses exhibited here and in other similar threads,
#1 zinc and Phosphorus go hand in hand. Oil companies have been cutting back on the use of Zn and P as anti-wear additives. This reduction of phosphorus content is a mandate issued by API, American Petroleum Institute, who is in charge of developing standing standards for motor oils. Zn and P have been found to be bad for catalytic converters. In 1996, API introduced the API SJ classification to reduce these levels to a maximum of 0.10% for viscosities of 10w30 and lighter. The 15w40 and 20w50 viscosities commonly used in Porsche engines did not have a maximum phosphorus limit. The API SL standard maintained this higher limit but with reduced limits for high temperature deposits. With the API SM, phosphorus content less than 0.08% was mandated to reduce sulfur, carbon monoxide, and hydrocarbon emissions. The biggest difference between the API SM and SN standard is that with the subsequent SN standard now mandated a max phosphorus content of 0.08% for all motor oil viscosities, not just the 10w30 and lighter oils the previous API standard limited, and limits for high temperature deposits are reduced, requiring added detergency for increased engine cleanliness allowing for longer drain intervals. Most modern oils are not backwards compatible with older engines for these reasons.
To offset the reduction of zinc and phosphorus levels required by the EPA, boron as well as molybdenum disulfide, among other friction modifiers, has been added to modern oils. The addition of boron, when in the presence of ZDDP, does boost the anti-wear properties and although considered an anti-wear additive, the use of "moly" has been truly limited only to increasing fuel economy requirements of the CAFE (Corporate Average Fuel Economy, enacted by Congress in 1975). These additions do not completely address wear issues of older vehicles that require higher levels of Zn and P.

#2 it is only the API 'Starburst' oils that have mandated ZDDP reduction, oils w/ the older API donut symbol can do what ever they want



#3 if the oil manufacturer you use doesn't provide the info they must be assumed to be using the reduced levels of ZDDP, whether mandated or not

#4 break in oil needs high ZDDP in the 1400ppm + range, but above ~2000ppm long term wear problems arise

historical ZDDP levels can be informative ie before the current ZDDP tempest

M1 API SH 15w-50 circa '93-96 1095ppm P, 1427ppm Zn(I don't have the specs for previous years but they would have been in line w/ the SH specs)

M1 API SN/SM current 1200ppm P, 1300ppm Zn

M1 API SJ 20w-50 1600 ppm P, 1700PPM Zn great break in oil!!

issues w/ cam wear became evident w/ the reduction to 800ppm ZDDP

1000ppm zddp can be considered a floor

Kurzheck

I run Total in my '74. My tech swears by it and it's been great. I run their synthetic in my '05 Carrera as well.

BER

Very good information Bill...as usual.

Thanks!

sugarwood

I've run VR-1 and Kendall, but I switched to a Synthetic oil on my last oil change.
No leaks. Just another internet myth.

In the winter weight oil thread, the most common response was Mobil 1 Synth. 15w-50.
It also seems to have a ZDDP content of 1300.


https://mobiloil.com/~/media/amer/us...pecs-guide.pdf

Well, I changed my oil to M1 Synth 15w-50.
I noticed these these markings on the jug, so it's not just generic oil.

Notice about ZDDP


"Race proven" was not on the other weights.

r911

...

spanky

I have no clue if its the best oil,or not, nor am i sure of the unit of measurement reqd to say its the best oil. I know Mobil 1 makes a good product and I trust it!!.
I use Mobil 1 V twin 20/50 in my 911s, 968 and my 951 turbo, I am very happy with the results after many yrs of use!!

LexVan

Mike Murphy

r911

not all that relevant to the type of valve train used in an air cooled pcar motor

Mike Murphy