Engine problems associated with sludge.

BMW wasn't mentioned but Mercedes was.
http://select.nytimes.com/gst/abstract.html?res 0611F63E5B0C778CDDAB0894DF404482
TECHNOLOGY; Engine Sludge: When Good Oil Goes Bad
FOR people buying a used car, there is a very important but rarely checked factor to consider that goes beyond kicking the tires: original sin. Some best-selling models appear to have an increased risk of serious mechanical problems, particularly if scheduled oil changes were not made during the vehicle's ...
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"grinder"

Even if they were made, the schedules themselves these days may be the cause of the problem. Ever since BMW started offering "free" maintenance, the schedules were greatly extended... what is it now... around 15K miles when the light comes on on the dashboard? Depending on the circumstances, that may be too long. If you're only planning to keep the car until the lease is up, then I guess you'll be OK, but if you want to hold on to it longer, you may want to cut these intervals in half. Shorter still if you're using mineral oil.
Pete
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Actually, if the circumstance makes 15000 too long, then the light comes on sooner. The light seems to be aware of the "circumstances." It knows engine start cycles, and if the trips are stop-n-go or freeway travel. All of this feeds into the algorithm that tells the light to come on. With advances in oil and metal over the past few decades, running oil for 15000 is okay.
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"Jeff Strickland"

On many BMWs the algorythm is a simple measurement of amount of fuel burned, but it is a clever one nonetheless. But even if the circumstances are severe, it usually doesn't come on sooner than say 10-12k miles. I've seen UOAs of the BMW Castrol 5w-30 oil after 10K miles - it didn't look all so great. I agree that there are better oils out there that can go the distance though.
Pete
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It depends upon the car. BMW settled on a system that measures fuel burned only on the E39 and E46. It trips a light every so many liters. Evidently MPG relates quite closely to engine service. So a highway miles car gets the oil change around 16K+ (my 530 around 16.5) and an around-town 8 cyl around 12-13.5K.
Probably not as good as adding a cold-start count, average trip miles, etc into the equation. Allegedly, some cars examine the oil for condition (opacity? More junk in suspension, more chance the filter and additive package are near their limits? ... Don't know). Evidently the newer cars, E60, 90, 92 etc work a more elaborate analysis ... whether they do or not, they display a countdown mileage to oil change vice just a sequence of lights.
I'd agree 15K with lots of long trips is fine. OTOH, 7.5K with lots of short trips might be a wiser change interval. I'm inclined to think that short duty cycles reduces the oil service interval more than anything else.
R / John
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<major snippage>
"Evidently the newer cars, E60, 90, 92 etc work a more elaborate analysis ... whether they do or not, they display a countdown mileage to oil change vice just a sequence of lights."
The later E46's also have a count down mileage indicator. My '05 is presently sitting on 1,823 miles until Inspection 1...and there is only 24k on the odometer.
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Not just the later ones as my '99 328i (1st year E46) has the mileage countdown. Mine starts on 15,250, and calls for service after 15,500 to 17,500 miles with mixed city, suburban and highway miles.
Tom K.
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I agree, but the mfg. offers and supports a warranty based on the longer miles. If there was going to be a problem that shows up within the 0.warranty period then I am confident they would shorten the interval to reduce the warranty exposure.
I would not be comfortable on first noticing that the oil change interval was so long, but after finding out that the oils today are not the oils used when I was a kid and that the metal technology was remarkably improved, and taking into account that the mfg supports the warranty based on the longer intervals, I'd not be concerned.
In any case, I would NOT change the oil every 3000 miles, like I learned to do as a kid. I have no problem today with a 7500 mile change interval, or longer. Your mileage may vary.
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on a related note, my recently acquired '95 E38 (103,000 kms) had regular oil changes by the past owner but I'm considering switching to Mobil1 or Amsoil synthetics in the spring. First do you think this a good idea and if I do should I flush the engine before the new stuff goes in. I wonder too if I should stay with what the engine 'knows' your thoughts? thanks
Maurice

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First, I have no real evidence to back up my position but I was always told "start with non-synthetic - stay with non-synthetic." At least if the non-synthetic was used for 15k-20k miles.
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"grinder" wrote

Urban legend.
Pete
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So deposits caused by using non-synthetic oil will not be removed by synthetic oil?
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IIRC, that was an issue some 50 years ago with detergent vs. non-detergent oils.
Tom K.
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"grinder" wrote

They might be, but I don't see a reason why not to switch to synthetic because of it. Afterall, do you want to keep sludge inside your engine?
Also, modern day mineral oils also contain additives/detergents that prevent deposit buildup.
Pete
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