| PeteKz |
03-06-2023 05:12 PM |
About 7 years ago, I was at Carlisle for a weekend Ford show. Joe Gibbs Driven had a tent set up. The presentation was given by their chief engineer (I forget his name). The main point of his presentation was to NOT use any aftermarket oil additives, and just as importantly, why. It turns out that there are several dozen different formulations of ZDDP, "zinc," or whatever name you use, as well as the other additives (detergents, friction modifiers, etc.). The oil additives have to be designed to work together, so that the one does not interfere with the other or actually cause it to precipitate out. Then you end up with less ZDDP or other additives than you started with. Therefore, don't user any oil additives. But you already knew that.
Of course, when you have access to a guy like that, you hang around after the presentation and ask more questions! It was a fascinating discussion, all the details of which I can't fully recount, but some important points: the highest pressure and wear points in an engine typically are the cam and follower contact, and the rocker to valve stem. These places have high loads that concentrate in a line or even point, with a wiping motion that tends to wipe off the oil film, so ZDDP is crucial at these points. Newer engines are designed with roller followers on the cam in order to reduce these point/line and wiping motions, because EPA regs have increased the time that emissions systems must be warrantied, and the zinc poisons catalytic converters, so in newer oils the ZDDP had to be reduced, forcing the followers to be redesigned toward with less of it.
Another important point: The break in occurs in the first 100 miles, usually much less, because engines are now manufactured to tighter tolerances, and the cylinder wall finishes are smoother, so the rings seat sooner. In addition, most new engines are now test-run on a dyno before they go in the car, so that part of break-in already occurs before a new vehicle even reaches the customer. The journal bearings (mains, rods, and cams) should not break in, because they should always be floating on an oil film. Some other parts may see high loads, such as timing gears or chains, but usually not if well-designed. Driven offers a break-in oil, but he said that for new cars and trucks it's not necessary. If you are building a racing engine with cast-iron and rougher cylinder finish or using older cams and lifters, then use it.
Well, as everyone now knows, our old air-cooled 911 engines weren't designed for low-zinc oils, so we want to find oils with high ZDDP levels. Diesel rated oils became the initial go-to oil for the older hobbyists, because diesel engines didn't have catalysts until recently, so they had higher levels of it. However, as most of you also know, in recent years, diesel engines have been fitted with catalysts and Diesel Particulate Filters (DPF), and consequently the zinc levels have been reduced somewhat. So just picking any old diesel rated oil no longer guarantees high ZDDP.
To further complicate things, the oil manufacturers change their oil formulation from time to time, and don't make widespread announcements about it. It's not a trade secret, but you have to go to their websites and look up the oils and see whether anything has changed recently.
Since that's a PITA, I've been using the Ford Motorcraft brand 15W-40 diesel oil for Powerstroke Engines. I don't have the experience that some of you do with building 911 engines for decades and seeing how long they last and what wears out, or what wears out in racing, so If you have good results with a particular oil, I won't argue. But I chose the Ford Diesel stuff because it says right on the bottle, "Contains more than 1000PPM of phosphorus (that's the P in ZDDP). Not for use in catalyst-equipped engines." Yeah, that sounds like the good stuff to me. I was using Delo for a long time, and still use it in some other old cars, and I can't say I ever had a problem with it. But the label on the bottle doesn't tell you much. So I lean towards the Ford Diesel stuff. Especially when it's on sale at Walmart!
Anyway, some things to think about when you go shopping for oil. And if in doubt, check the web site for the oil manufacturer.
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