A tranquil reflecion on the eternal oil debate

livi · 03-02-2007, 09:44 AM

Following the regularly repeated oil debate threads, I wonder how much sense it makes in the end. A bit too low or high a content of this and that additive.

Many of our beloved 911´s spent their first 100-150 k miles with owners who probably did not have the passion and care that we have. Driven their (now our) cars like they stole them - from cold start.

The engines in our 20+ years cars had to endure much lower quality oil and probably longer change intervals during their perhaps first 15 years / 100-150 k miles.

Our beloved Porsches must feel they have come to spend their last year before retirement in Sports car´s Heaven! Their last miles on this earth they are suddenly treated with a conscientiousness bordering on neurotic regarding choice of oil as well as meticulous, painstakingly short change intervals.

All in all, I wonder how much of total engine wear is avoidable by this scrupulous fastidiousness on oil choice for our old pearls.

That said, I am as neurotic as any one else around here. I suppose it is called passion.. Porsche passion.

scottbooth · 03-02-2007, 12:12 PM

Hi livi,

I am not an expert on oil, and I certainly agree with your argument that regular (or obsessive) maintenance, combined with a general improvement in oil quality over the years, does a lot to preserve these old cars.

However, what I have gotten out of the recent oil related threads is that a lot of recently reformulated oils have less of the Zn and P additives that the older 911 engines need, particularly because of the types of rocker arms used. Some of the engine builders (and oil experts) have weighed in with support of this idea, both from the theoretical side and from observation of actual engines "in the field". The idea being that even with frequent oil changes, the cams will wear faster than before.

I am not sure if the oil formulations used when our cars were new just had lots of Zn and P, or if those oils had other properties that made the additives unnecessary. (I can't remember if the Zn/P issue affects all oils, or just synthetics. It does seem to apply to me, since I use Mobil 1, which per the new metrics seems to be adequate but not superior.)

Just something to ponder - in tranquility...

Scott

livi · 03-02-2007, 12:49 PM

I suppose there are valid facts - both theoretically and in vivo evidence in terms of quality. But what about quantity? Do anyone have a clue how much of these additives is optimal for our old engines? How much less is adequate and at what ppm will the wear curve cross the line for significant extra wear?

Kind of reminds me of some classic medical traditions. For example - most antibiotic treatments have traditionally been prescribed for a week (7 days. No more. No less). There are no scientific studies that indisputably prove that 6 days are less effective for most infections. Probably not even 5 days for some infections. Plausibly 4 and most likely 3. Etc, etc.

Not trying to be a smart ass - particularly since I have very rudimentary knowledge of this mechanical issue. Just trying to suggest a point - that very well may be totally wrong..

cnavarro · 03-02-2007, 02:57 PM

I'm not going to name names, but some well known shops have observed failures using the newest SM formulations first hand.

It is not only the cam/rocker wear (and lifter in the pushrods engines), but also a noticeable increase in bearing wear, especially rod bearings. Although very pronounced in race engines, this wear may take time to show up in a street engine. If we can prevent it in the first place, why not?

livi · 03-02-2007, 11:28 PM

Charles, I absolutely agree. Preventably wear should be addressed.

I think my reflections perhaps are too academic. In my line of work it is paramount to work with proved causality and known probability as well as ruling out cofactors and finally put everything in the perspective of expected gains and costs/risks.

In this case such calculations are not very valid of course as the cost and risk of choosing a reputable oil with the required amount of additives are not higher than any other oil.

I hereby rest my case.

Early_S_Man · 03-03-2007, 08:12 AM

Quote:

The engines in our 20+ years cars had to endure much lower quality oil and probably longer change intervals during their perhaps first 15 years / 100-150 k miles.

I'm not sure I buy that postulation ... 20+ years ago the use of synthetic oil was not that common, and the usual oil change interval was 3000 miles.

I don't buy the 'much lower quality oil' assertion, either! Fresh premium petroleum-based oil back then was probably just as good as now at basic metal protection, just the VI additives didn't last as long. I have been using USA racing oils for 39+ years, and oil related wear problems were unheard of in the '60s. Maybe I should dig up an article from Motor Trend about motor oil and additives that I used in a research paper my senior year in high school ... circa fall of 1967?

914efi · 03-03-2007, 08:59 AM

I subscribed to the 'cheap new oil is better than expensive old oil' theory also. Until recently. The new changes are meaningful, especially to us. The combination of new engine technology and new gov't regs have put us in the position of really needing to find the oil that will work with our older type engines. It seems (from following other threads) that the jury is somewhat out on whether it is primarily a break-in issue or a long term running issue.

livi · 03-03-2007, 09:34 AM

Interesting. I have read and heard over and over how much better modern oil is compared to twenty years ago. From threads on Pelican to renowned motor magazines.

If that is not the case - well, then I certainly have no case at all..

cnavarro · 03-03-2007, 10:15 AM

Well I tested oil from the 70s, actually Kendall GT, which was the highest regarded oil then, and it had levels in the 0.12-0.14% Zn and P. The oils are better, higher flashpoints, longer drain intervals, but that still does not negate the fact that the anti-wear additives are being reduced.

And yes, there are other additives that can be used in place of Zn and P, but every research paper I see clearly states that Zn and P are the best regardless.

livi · 03-03-2007, 10:38 AM

Are the additives more important in our old engines than in modern cars ?

movin · 03-03-2007, 11:20 AM

Bingo, give the man a cigar! Absolutely, how many air-cooled auto engines are being produced for consumer use today? Duh?

livi · 03-03-2007, 11:25 AM

Thanks Movin!

I apologize for my ignorance. I am trying to learn. This is not my line of education, you see.

Why then, is it that air cooled engines are more sensitive to the amount of certain additives ?

cnavarro · 03-03-2007, 02:03 PM

Newer "modern" engines use 4 or more valves, lighter valvetrain and less spring tensions, lower overall bulk oil temperatures, and so on. Huge differences when it comes to the requirements of a motor oil.

Additionally, most modern engines are designed with more modern materials and tighter clearances, allowing the use of lighter oils to help meet CAFE fuel requirements imposed by the Federal Government on auto manufacturers, sometimes at the cost of longevity of these engines. In turn, there are also longer emissions warranties and more stringent emissions which push for changes, like the new API SM. They aren't looking to make the engine last longer, just the emissions controls.

What I cannot understand is that the API clearly states that 10w40 and lower weights are only required to meet this standard, so why must an oil company, mess with a 15w50 or 20w50 formulation. 15w40 diesel and mixed fleet oils are usually rated using a different system, CI-4, CI-4 Plus, and now CJ-4, again reformulated for emissions.

The biggest culprit in modern engines is sludge from extended drain intervals and from oil contamination (not getting the oil hot enough to burn off the moisture content).