_Remi

Hi guys,

I was about to order some Brad Penn 20w50 to top off my 1993 964 (which I believe is running Rotella 15w40 from PO but I am planning on switching at some point). It says on Pelican that it cannot be used with catalytic converters but it seems that many folks here are using it, is that relevant?



Thanks!

HDA

Earlydays

I read from a reliable source that it will shorten the life of CC's, but it takes a lot miles to have an effect, like 50K plus.

Bloose993TT

Never heard of that. I guess I would rather replace a cat than rebuild a engine. They changed the name to Penn Grade btw.

newsboy

Almost all oils worth using in our non-hydraulic lifter engines contain a higher level of ZDDP for protection. I have 85K on my car with no signs of degradation to the cat. Don't think it's anything to concern yourself with.
But if your cat does give up the ghost, replace it with a 200 cell cat for a little more power and sound.

dlpalumbo

Or you can consider this blog where writer claims amount of ZDDP is not reliable measure of protection. He seems to have not only experimental but real world data to support his claims.

For an air cooled engine you need sufficient viscosity. The writer goes into some detail about this in his posts. I am considering Castrol GTX as a good alternative as it outperforms Mobil1 15w50 with lower ZDDP level.

The writer has way more creds in area than I have so its difficult for me to argue with his results.

Dan

boostedt0y

Just do a cat delete and then you don't have to worry about the cat going bad

-nick

GDOG8

_Remi

Ok thanks guys, I went ahead and have already received the goods. It is indeed rebranded (and will be a good excuse to upgrade to a sports cat if need be).

Steve Weiner-Rennsport Systems

FWIW,.....

After 44+ years, I have NEVER replaced a cat because it was poisoned by ZDDP.

Cats fail due to excessive heat caused by lean or rich fuel mixtures.

I suppose if an engine was burning excessive oil (due to guide wear, blowby, or high oil levels in the tank), it could happen, however I chalk those things up to human factors.

Bill Verburg

The issue the conflict between the US EPA's requirement of 100,000mi cat life and simple chenistry

In use the P in ZDDP is transported to the catalytic surfaces and over time interferes w/ the cleansing action. They just gradually become less efficient. The protective part of ZDDP is the Zn which also is used up over time, change your oil regularly is the solution to that.

Generally an owner is more concerned about engine MTBR rather than cat efficiency over time, the obvious exceptions are those that live where there are annual sniffer tests, which will detect the reduced catalytic efficiency eventually. From early experience when ZDDP reductions first became widely noticed a min of ~1000/1000 seems to be necessary, M1 FS 0w-40 @1100/1000 which was recommended by Porsche for many years is right at this minimum.

That said too much ZDDP is as bad as too little, There is no need for 1700/1700 and up except as a break in oil.

A Sweet spot oil is 15w-50 M1 @ 1200/1300 ppm P/Zn. Some advocate M1 V twin @1600/1750, The only reason not to is the cat and pocket book wear

There are certainly other fine 15w-40 15w-50 oils out there that have specs similar to M1, examples are PennGrade 15w-40 @1500/1400(on the high side)

Do you r due diligence, If the ZDDPs levels are specifically iterated they are likely too low.

One last personal experience, a friend ruined his '93 964 after only a year or two of using Castrol 0w-50, it's unknown whether this was ZDDP or weight related

Mikel Whois

i used Royal Purple HPS with ZDDP in my 08' Subaru Legacy & also in my 06' Nissan Titan both w/ around 150k already on them prior to adding ZDDP (which is about where stock cats will normally fail if there are things like oil blow-by occurring, which at those miles there typically will be, especially in Subaru's but i digress) both cats failed before driving 30k more miles after adding ZDDP. My best guess is that the already deteriorating converters wear was further and rapidly exacerbated by the addition of ZDDP. Cool with me though, easy way to decat both of them since they were already cooked all i had to do was disconnect the pipe and blow it out by revving the engine in the Subaru. The Titan needed a little more persuasion via drill bit.. but not much. I wouldn't reccomend doing that to your Porsche though as almost any Porsche is better and more valuable all original and/or fully restored. Though an old ragged-out one might be fun as a project to track, it would still be painful decimating such a brilliant work of art. Porches to me have always represented perfection in their purest form.