68post

OK. Then that would be yet another "German Castrol"/ "European Spec" and imported into the US. My BMW doesn't call for that particular oil and I wasn't aware of its existence.

Probably a great oil for someone's track day, bet you could really abuse the equipment and this oil would take it in stride.

Jim Rogers

billo--

I'm wondering why in the first post you say:

You're making the strong implication that SN/M oils (800 ppm zddp) are not really acceptable in stock flat tappet engines.

How do you account for the Sequence IIIG tests that show that these oils pass the ACLW test easily under the 60 micron limit (usually at around 37 microns)?

Totally agree that for aftermarket/performance applications, more zddp is better. But the data appear to show that, for stock engines, there is no need to say they "might" work or "appear" to work or you need "tired springs."

billla

I'm making a flat statement that SN/SM oils are not acceptable in any flat tappet engine based on my discussions with cam companies and broad anecdotal evidence.

I'm not an engineer and won't pretend faux knowledge by Googling that test Everything I've written was from cam manufacturers and backed up from broad but openly admitted anecdotal evidence.

I said nothing of the sort. I simply stated that an engine that has a low-lift, easy ramp cam and low spring pressure may not experience the same types of failures we see in more modern cam profiles and higher pressure springs. This was simply to acknowledge the anecdotal evidence provided by the "I've been running SN/SM oil for a long time in my NNN and it's worked fine!" crowd.

As always, folks are welcome to run whatever oil they choose based on whatever research, guidance and engineering data they like. I simply collected and collated information across sources and maintain a list of oils that state specific support for flat-tappet cams and are above the SL specification for ZDDP. I offer that given the cost differential and the value of classic Corvettes, I personally see little reason to take a chance.

Jim Rogers

I quoted you directly-- those were your exact words.

With all due respect (and I mean that sincerely as you've put a fair amount of effort into this over the years), I don't think it's reasonable to rely on anecdotes and information from manufacturers of extreme, high performance cams to say that SM/N oils are "...not acceptable in any flat tappet engine."

Why rely on anecdotes when there is an explicit test designed specifically to address this issue? Why maintain ignorance of the fact that all SN/M oils easily pass the Sequence IIIG test that was specifically designed to verify that oils do not allow undue wear of stock valvetrains? Why rely on cam manufacturers who are not making stock cams? While the more extreme cams they sell might legitimately benefit from high zddp oil, they also have every incentive to cover their asses by recommending the highest levels of any additive purported to protect their product.

And, more importantly, why reinforce a myth with anecdotes over data and then say "...folks are welcome to run whatever oil they choose based on whatever research, guidance and engineering data they like" when the fact is that you are proffering this thread as research and guidance? As the originator and maintainer of this thread, it is incumbent on you to make sure that your advice is fact-based and sound. It is a contradiction to maintain a potentially false narrative with strident arguments over many years and justify it with a disclaimer that you are not an expert and people can rely on whatever sources they wish.

The above is probably coming off as far more harsh than I intend as I am also not an expert. I am one of the many trying to resolve whether 800 ppm zddp is ok for my stock Corvette engine. SAE testing sequences appear to indicate that it's not a problem, people on forums indicate it is a problem. I was hoping this thread might resolve the question, instead it appears to repeat anecdotes as justification of the forum position and doesn't even mention, let alone consider, the SAE testing side of the debate. The result is an unsatisfying thread for those interested in the relative merits of both sides.

I think you should consider modifying your statements about the need for >1000 ppm zddp in stock engines. Either provide evidence that the SAE testing sequence is incorrect or provide full disclosure in the first post that there is legitimate engineering data that shows that SM/N oils are fine for flat tappets on stock cams but you simply disagree and are choosing not to present or discuss it.

billla

No, they're certainly not. Show me where I said "you need tired springs." Why in the world would anyone "need" tired springs? Again - you can read it any way you like, of course, but I explained what I said, my words are there and your restatement of it was flatly incorrect.

Is the venerable "390" cam an "extreme, high performance cam"? I don't believe so - yet this is made today by CompCams, and they recommend a pre-SM/SN oil.

Jim, I can tell you have an axe to grind here and honestly - I'm not the honing stone You note that you're also not an expert, but apparently have read some papers - and so you're right and I'm spreading a "false narrative" and I'm disingenuous for posting information consistent with information provided by virtually every cam manufacturer.

In the end, the only thing I see you advocating for is cheaper, more readily available oil. Is there another reason that a classic Chevy owner wouldn't invest a few dollars more in an oil change, if nothing else for peace of mind? Regardless, your post is here with information for folks if they choose to give it credence.

I don't see a need to engage on this; I'll continue to suggest that classic Corvette and other muscle car owners spend a little more money and go through a little more effort to protect their investment.

H P Bushrod

Closed per OP's PM request.