IXLR8

But what were the level decreases between 1993 and now?

As for the 0W-50 that you would be sticking with, I take it you are referring to the Mobil 1 Racing which is "not recommended for street use", according to that list. I take it they state that because there may be some disadvantages associated with that oil.

Just what I mentioned earlier in one of the posts above about Zn being a last line of defense...from that article...

^^^And that happens when the film of oil has broken down and that is where I believe the Zn comes into play...the last line of defence. Oil as far as I know has two main purposes; to prevent metal to metal contact and to remove heat...besides not foaming, preventing corrosion, etc.

I'm not on the track or running my engine to extremes. I think M1 15W-50 is fine. Looking at the cam lobes on my 993, they look like they just got installed.

IXLR8

Also note that what is good for one application, may not be good for another.

Back in the early 70s, racing two-strokes used castor oil in the pre-mix. It had one great smell when a TZ went by. It was also a very good lubricant...for the purposes of a race. I believe the long term downside was varnish build-up.

Steve Weiner-Rennsport Systems

Alex,

Modern 4-valve engines use soft valve springs due to the reduced mass of the valves and as such, do not load the camshafts and followers as much as 2-valve engines do, all things being equal.

Thats why SM/SN oils do OK in these types of engines.

IXLR8

Steve, mind you, when I had the valve covers off the 993 to do the valve cover seals, the cams lobes looked like new as well. I couldn't see the rocker surfaces though. Maybe I'm lucky or my car hasn't seen a hard life.

vincer77

I am sure the disclaimer is due to the poisoning of the catalyst problem. But maybe there are other differences.

FlatSix911

Hi Alex, I agree with using Mobil 1 15w50 for the street and 0w-50 for the track.

flyingchappy

When I had my car in for some service this year at my mechanics shop he used M1 0-50w when I asked him to replace the oil. I've driven a total of 1k miles since then. I'm not a chemist but I do understand the importance of using the correct oil for differing engine types and driving purposes, but now I am concerned that I'm at risk with this type of oil. Should I go replace it with 15-50 at the next available opportunity?

IXLR8

You're probably spot on and here we've already been talking about that aspect. I was thinking additives that might have be time dependent which probably is not the case or reason...sort of like the two-stroke oil I mentioned a few posts up.

IXLR8

If you go through this thread, you may have noticed someone stating that the Zn level was decreased to maintain the life of the catalytic converter, which is true. By using the oil that is presently in your engine with the higher Zn level, I don't think you are risking the engine...only the $$$ catalytic converter $$$.

Steve Weiner-Rennsport Systems

Actually, it was mainly the Phosphorus that was reduced to extend the life of the cat.

There is a ton of detail information on these subjects available from SAE that among other things, explains precisely how Zinc & Phosphorus work, what happens when there is too much of these elements, and many other closely related subjects. I spent about $450 a few years ago on various papers to get an education on this very complex subject that was most enlightening and I'd encourage anyone wishing to understand this to do the same.

IXLR8

Now you know why I question so much of what I read on the web.

I heard and read that it was the Zn.

NC TRACKRAT

Per IXLR9: "Back in the early 70s, racing two-strokes used castor oil in the pre-mix. It had one great smell when a TZ went by. It was also a very good lubricant...for the purposes of a race. I believe the long term downside was varnish build-up."

+1! Ahhh, the smell of burning castor bean oil! Nostalgia! If you go to vintage races, every once in a while, you can get a whiff of it. I can close my eyes and do a time trip to the '50's and '60's.

Mike_A

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Blendzall has a fuel additive made for new engines (and old I suspect) with the same castor oil fragrance....it is marketed as an additive for top end break in.....I don't know what it would do to the cat on the 993 if anything, but I use it in my old 911 and 356....

Glenn Evans

Hi all! I hope you don't mind an interploper from the 928 forum reviving this thread. I found it when searching for Steve Weiner's latest posts on oil and wear.

Michael Grant concludes that wear problems mostly are the result of incorrect run-in, and that flat tappet engines can be run on oil with zinc content of 0.06 to 0.08 per cent once they are properly run in.

This is not the experience of an independent Porsche mechanic here in Sydney who, by the time he was drawn into the oil debate in 2006, had been seeing accelerated wear for some time, and had associated it with the use of light synthetic oils, including on older engines which previously hadn't shown untoward wear. He, however, had continued to use the oil which Australian dealers had adopted in the 1980s to withstand the demands of the 930, and engines run continuously on this showed no observable wear. I should add that it later became apparent that the reduction of ZDDP levels in oils was associated with greatly accelerated wear, not least through the writings of Charles Navarro and Steve Weiner.

Stever Weiner has said that he runs his engines in on his dyno so that he can control the process.

Steve, was this your practice before you became aware of the reduction in ZDDP? If your engines suffered wear after you had run them in, but they then were run on a low ZDDP oil, that seems to me to be more evidence that flat tapper engines cannot run on oil which is low ZDDP, even after run-in.

techman1

My concern, (although as a consumer, not a pro) is what seems to be a broad grouping of all of the "flat tappett" engines together, and stating it is good for one, it must be good for all. My '73 Olds Cutlass, that made a wonderful 180 hp, had a low compression, with a detuned v8. Maybe the low zddp would not have affected it, who knows.

What kind of loads are our lifters and cams seeing, versus the old hydraulic valves, and the old profile cams? I feel it is not so much the style of lifter, as much as the pressure generated.

Comments?