I may have discussed this briefly in a previous post, but I thought an
update may be of benefit.

The car is a 2006 S 4.2. Since new, I have had an oil analysis performed
at every oil change. The car now has 82K miles. For many years, I flew
for one of the major airlines and the mechanics acquainted me with the
oil analysis concept. When you have 4 to 6 million hanging out on a wing,
you tend to want to monitor it's health. If it starts shedding metal, etc.
you want to know NOW! Crashes are expensive and bad for business.

Now, I'm "old school". I tend to change oil on the average about every
5,500 miles. (Please, I don't want to debate this issue) I do it because
oil is relatively inexpensive, and, while the lubricating properties of the
oil may not deteriorate for 10 thousand miles or more, the additives do.
And, I want to monitor the engine's health, the air filter, possible antifreeze or fuel contamination, etc.

Full disclosure: I don't know anyone, not married to anyone,etc. at the firm that I use/recommend. Furthermore, If you're going to dump your
car before the original factory warranty expires, read no further; you
would be wasting your time and money. Any incipient problems will be
the next guys problems.

How it works. The firm sends you a preaddressed plastic container
that contains a smaller plastic container. You give the small one to
your mechanic, and he "catches" about 60 cc of oil during the drain
procedure. You fill out the form, add about $1.20 in postage, and
usually have your report e-mailed or sent to you within a week.

The analysis. Twenty minerals are measured ranging from aluminum to
zinc. You also get a viscosity, flashpoint, fuel%, water%, antifreeze%
and insolubles%. Thus, if you have fuel or antifreeze in the sample,
you know you have a problem. High percentage of insolubles? Your
air filter has probably gone South, or you have an induction leak.

For an additional fee, the firm will measure the remaining additives
which will help you determine how long you can actually go between
changes. Oh yeah, they also give you a comparison to the results
of all similiar engines.

Where the hell am I going with all this? Well, in the future when you
read my rants about Jaguar quality and its service, keep in mind that
they appear to make a damn good engine. Thus far, at 82 thousand
miles (90% of which are highway miles) there are NO, NADA, ZIP, signs
of wear metals in the oil. No fuel, no antifreeze, no nothing. The low
silicon level shows good air filtration. Because of the remaining percentage of additives, the firm believes I could run the oil to 8,500
miles without problems.

Also keep in mind that this vehicle is driven in perhaps the lease hostile
environment in the US of A. Most of its miles have been in the Pacific
Northwest where the temps rarely get below 30 and above 80. Rain?
Sure. But that's fresh water. It would be interesting how this engine
fares in the rust belt, or places like Northern Minnesota.

 

That is very interesting stuff. How have other engines done? I would expect any modern engine to go well beyond 100k before anything signifanct shows up. It's all the electronic stuff that will give you problems.

 

And as a 31 year career employee at the very company that designed, manufactured and supported the engines you trusted you life to, please take this in the context in which it is intended.

The science of oil analysis is far more complex than taking a single sample once every few months or years. Without samples taken at weekly if not daily intervals and the establishment of a initial base line, the results are virtually meaningless. Any one sample can give a false positive or worse, a false negative.

I'm sure that the airline you flew with conducted the oil sampling and trend monitoring IAW with the MRB document and the OEMs directives which mandates a trending program for this as well as engine performance, but the program you are discussing with the present results doesn't really establish much.

I also disagree with your assumption that oil additives are depleted at a level less than the OEM recommended interval. What is your source for this?

 

Back in the 1960s in UK there was a thing called "The Mobil Economy Run" in which quite ordinary cars were driven by extraordinarily (try saying that when you've had a few) mean economy drivers hell bent on squeezing the last few yards out of a gallon of petrol. Some of the achievements were quite amazing. And this in the days of carburettors etc.
One enterprizing outfit even went to the extent of fitting radioactive piston rings to a Triumph Herald (997cc., overhead valve pushrod engine). This outfit then checked the engine oil for signs of radioactivity -- it might well have been Mobil themselves.
It showed up that 90% of the ring wear happened during the warmup phase, so one could assume bore wear was similar. The reasons given were that because the fuel/air ratio had to be rich for cold-running, some of the petrol condensed on the cold cylinder walls, WASHING OFF the oil film. This was the first indication to me that long distance running with engine at operating temperature was the best way to get a long life from it, since proved many times over. I have bought many cars with quite hefty mileages, and the engines have not been a problem, and consumed no oil between oil changes. My XJ6 done 155,000miles and would obstinately not use any oil. This car ran on propane/LPG and of course had no cold-condensation effect. I think diesel engines don't suffer from cold wear as any unburnt fuel happens to be a lubricant anyway.

I have a question for Cliff. Since I'm one of those extraordinarily mean drivers who want to squeeze the last few yards out of every litre of fuel (not gallons anymore boo-hoo) I wonder why when I've changed engine oil to full synthetic of appropriate xx-W-yy grade from mineral oil, the mpg. figure takes a bit of a nose-dive? This has happened on more than one car. Does it need to "wear-in"? Or are some engines not synth-friendly? Nowadays I always use a mix as my engines being always diesel have turbochargers with hot bearings.
Leedsman.