Latest engine oil grade SM promotes cam wear

TonyD

I heard about this through the GTO Association of America, but the latest grade of engine oil, SM, does not contain ZDDP. This molecule, which was in quality oils for the last 70 years, reduces sliding friction on flat tappet engines on the cam surfaces and also in the crank and rod bearings. I've read of camshafts wearing out in 900 miles!
Previous grades had 0.12% (SG) and 0.15% (SF) ZDDP by weight.
Apparently new cars with roller rocker set-ups don't need ZDDP and the zinc and phosphates in the additive can degrade catalytic converter life, so its been done away with.
My daily driver is an 87 El Camino with 326k miles and I'm not ready to give it up!
There are ZDDP additives available but that means the cost of an oil change just went up by $10 ($9.95 for a 4 ounce bottle).

Does anyone have any good news about this!?!

elcamino74guy · Posted: Mon Jul 14, 2008 5:49 pm Post subject:

This has been discussed. See the following topic..

SM Grade oils

I know I still see lots of oil on the shelves of my local auto parts store that are SE grade.

Happy

_________________
74 El Camino Classic - project car #1
96 Camaro - RIP, Traded 10-16-2007

2008 Mustang GT, It ain't a Chevy but at least it's American!

TonyD · Posted: Tue Jul 15, 2008 10:07 am Post subject:

OK - Thanks! I did a search on ZDDP but didn't find anything.

I tend to buy oil in the 5 Qt containers and haven't seen the older grades, and besides, they won't be available forever.

I read through the string and several links but still have a question: Assuming this is a real concern and I should use a ZDDP additive to prevent cam etc wear, does that mean I'm going to ruin my catalytic converter?

elcamino74guy · Posted: Tue Jul 15, 2008 8:26 pm Post subject:

I don't see how unless you have excessive blowby or your rings are shot.
In that case it wouldn't matter what kind of oil you were running.

Normally you shouldn't have any oil getting past the combustion chamber.

Happy

_________________
74 El Camino Classic - project car #1
96 Camaro - RIP, Traded 10-16-2007

2008 Mustang GT, It ain't a Chevy but at least it's American!

TonyD · Posted: Wed Jul 16, 2008 9:15 am Post subject:

Thanks for the reply!
That's what I was thinking - unless the oil is getting into the exhaust, the converter wouldn't know the difference. But I was surprised to see this in the literature I was reading. One of the reasons they gave for eliminating the additive was that new car manufacutrers needed to warranty the converter for 100,000 miles and this could degrade that life.

I change my oil every 3000 miles and its down about half a quart so I shouldn't have a problem.

Thanks again

MarkZ28 · Posted: Mon Jul 21, 2008 11:24 pm Post subject:

Haha, what cat convertor? Mines been gone for a couple years or more. Deisel oil still has what you need in it, Rotella T and Delo 400 are a couple examples you can still get at WalFart.