We've been speaking of oil change intervals on an other thread.

I'm curious: How many of us take a sample of the oil at each change and send it off for analysis?

 

Only if there was a reason to do that. I change oil every 6000 miles or 1 year, whichever is less.

 

+1, And even then I fail to see what it is going to do for anything?

 

Doing an oil analysis with every change provides a baseline that lets you recognize certain types of engine problem before they lead to damage. Rather like a blood test actually.

We do them regularly on aircraft. The private owner of a light aircraft really can't afford not to do oil analyses because the cost of a preventive action may be a few hundred dollars, but the cost of finding out about the problem with overt symptoms can be in the thousands easily. Or an engine stoppage leading to loss of the aircraft. Well, possibly the people inside also, but like Porsche owners, the vehicle is often the first concern.

 

It makes sense for aircraft, not sure about P-cars. Would rather change more frequently than bother with analysis. To each his own though, do what makes you most comfortable.

 

The engine goes on an airplane, there is a lot more potential problems that need to be dealt with in an urgent manner, like where do I land. A car, coast it to the curb and call a tow truck.

My point is if the engine is showing signs of wearing, I doubt that Porsche would do anything about it until it is causing a problem.

 

I just consider it an inexpensive science experiment. Curiosity is all. I ordered at kit and for $30.00, seems like good clean fun.
After all, unlike my flying days, in case of catastrophic mechanical failure I can just pull over.

 

I think I wasn't clear. You don't analyze the oil to see the oil's condition. You analyse it to identify the contaminants the oil is carrying away from the engine. For example, ... damn, too tired... mind is going I guess. A certain metal is characteristic of the alloy used for main bearings, another for the valve guides and so forth. Can't remember which ones right now. Analysis determines how much material is being lost from each in normal conditions. And yes, it is always some. Carrying away contaminants, from microscopic metal particles to gasoline is one of the important roles of oil in an engine.

If the content of main bearing metal starts to rise, you are at risk of running a main bearing. Last time I checked one, I believe about twenty typical contaminants were sought in the lab analysis.

It's all computerized analysis of course. It probably costs no more than one additional quart of oil.

Once again, you don't do it to extend the interval between changes or to evaluate the oil itself. This is what you do when you do change the oil, whenever that may be.

And no, it isn't different for a Porsche engine than any other, except perhaps to be more important since Porsche engines have a higher specific output than do most.

 

Actually, I was talking about my own car, not Porsche's. I don't care what they do with their own cars. They can afford to replace whole engines after they fail. The rest of us are better off taking preventive measures to save the engine we have, since a whole engine surely costs at least twenty grand, and probably closer to thirty.

But as you say, each to his own. Modern engines driven casually rarely fail short of 150,000 miles and often much more. This is only something to consider if you do track days or otherwise exercise the engine to its full potential.

 

I doubt that a lot of the traditional engine repairs are even done anymore. Most manufactures make the parts more then whole and do a block swap and rebuild themselves rather then the dealer or independent mechanic doing it.

 

What he said! Not that I haven't crossed through some neighborhoods under GPS guidance that made a forced landing in an exotic seem more dangerous than a Cessna going down in the Northwest Territories, but basically you can almost always get a sick car to a halt with everyone walking away. Or... running as the case might be.

But it is another way to have an excuse to play with your car in the garage. And if it saves you twenty thousand dollars some day, what the hell.

Given the reliability reputation of Porsche engines, it probably won't ever be a critical aid, but it is interesting to track the pattern of the engine's wear as it ages.

 

I get the sense that both of you are talking about what Porsche would do if an engine failed under warranty. Those things do happen, often in batches when an entire lot of parts was out of spec (or spec'd wrong) at the factory, but that's what we call infant mortality. Oil analysis is for people who plan to keep their car past warranty, or just like to know what's happening "in there."

Warranty issues raise different cost trade-offs for the manufacturer. Acura pulled a entire transmission out of a Legend and replaced it with a new one for me because the factory wanted to analyse the early failure. (Actualy it wasn't failing, at least not yet, but it had worrisome symptoms. They agreed and replaced it to find out what was happening.) That cost them a considerably higher cash outlay, between shipping two transmissions to Japan crossing in mid-Pacific, and putting us into a high class rental car during the voyage. Any fully qualified mechanic could have pulled that transmission and replaced the failing synchro if cash outlay was the test. But factories need to know about all failures early in a model's life and the Legend was a very new release, as was the Acura badge whose reputation they wanted to build. Those are issues that go beyond shipping charges and rental cars.

Didn't Porsche lose a rash of engines in the 996 era? I wasn't an owner then, but I wouldn't be surprised if they built replacements at the factory -- using more efficient factory methods -- and just shipped them to dealers for installation. Removing and replacing an exotic's engine is usually a commonplace chore, whereas pulling it apart to fix something done wrong at the factory can be extremely awkward as well as going beyond the training of most field mechanics (as opposed to replacing a normal wear item, for which ethical engineers plan ahead even out to the third hundred thousand miles).

That's all well and good if you have an infant mortality and a factory on hand to do the work. Once you get past warranty, the owner is paying the freight and a whole lot of repairs become more reasonable than replacing the engine. About two years ago, we completely rebuilt the top end of an NSX 3.2 liter engine. Cost about seven thousand, whereas a replacement was about thirty for a new engine and fifteen for a rebuilt with core swap. I can't honestly say the thought of buying a replacement engine ever crossed my mind.

So we've probably identified the watershed: end of warranty. If you're planning to sell or trade your car before the warranty runs out and you don't do anything with it that Porsche would consider outside warranty coverage, then oil analysis is pointless. Interesting to a serious geek possibly, but pointless.

If you plan to keep the car until you drive the wheels off, or if you do things that might require you to pay for the repairs even before the warranty expires, then you're a candidate for oil analysis to keep track of what's going on.