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#61
04-10-2003, 05:26 PM
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Mark, while changing at 2k certainly doesn't hurt, and will probably help re-sale value... it is a waste of money. Even Rotella dino is probably fine up to 7.5k or 10kmi. That's when oil analysis comes in handy. At 2k your oil is almost brand-new, why change it?
The soot stays in suspension and while suspended, it is kept away from metal things. When the soot suspension limit is exceeded (usually 3-4%), then it causes wear. My analysis shows about 1% soot in 10kmi on both my 1987's, and about 2% in 7.5km on my 1984. That means I could theoretically go 25kmi on the '87 between changes, and 12.5kmi on the '84, and still have a decent safety margin. Just my $0.02... 
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#62
04-10-2003, 08:30 PM
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It is hard to understand how the "soot stays away from metal
things". I am not disputing or trying to have the last word. At 2k, my oil is so dirty that a small amount on the skin will leave a black spot requiring 5 minutes of scubbing to remove. It smells corrosive and is pitch black. Perhaps your engine has less blowby which contaminates the oil. Mine hardly appears new after 1k miles. OK, it may be a waste of money to change it every 2k. It is a mere 10% more than the cost of fuel for 2k miles. 1.90/gal @ 20mi gal (city+hwy avg)=$190 two gal Rottella=$13, I do the $5 filter every other change. I'll let it go a little longer between changes after reading about your soot analysis. Thanks
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#63
04-10-2003, 08:37 PM
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That's what scares most people - the oil is black, therefore it's "dirty"! Not true. That means it's doing it's job. Oil will appear black with an amazingly small soot percentage, something like 1/4 percent or so. That's why the only way to officially tell when it's "dirty", or "worn out", is with analysis. Your oil will turn black within 100 miles of the oil change because of the oil left in the cooler lines. MB specifically states NOT to drain these as damage to the cooler is likely. They designed the system to leave ~10% old oil in (total capacity is 9+ quarts with the cooler & lines). As soon as that 10% mixes with the new oil, it all turns dark black. This is perfectly normal. The filter is also good for at least 10-15k, from what I understand - it is NOT designed to filter out soot, btw!
HTH,
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#64
04-11-2003, 12:38 AM
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Quote:
Thicker oil would tend to decrease oil usage. It is suggested that the more wear or more mileage an engine has it would be well to use a thicker oil for the increased tolerances. However, in recent years I have not been able to locate anywhere a 20w50 diesel rated oil and have been using 15w40 or straight 40w in summer. Single weight oils will not break down as quickly as multi-weighted oils because of the added polymers which give oil the weight spread. And the greater the spread the faster oil loses its protection and is why I have not read GM recommending the multi-grade 10w40 petroleum oils for its diesels. My 300D is very happy however with 15w40 and uses very little between the 3500mi changes in spite of its 220,000mi. Just for your encouragement I hope you are able to find a 20w50 diesel oil. -Tom'  ')
__________________
'96 C220 138,000mi, '95 E300D 239,000 mi., '87 300TD 214,000mi '88 6.2 Turbo Diesel Chevy Conversion Van 253,000 mi.
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#65
04-11-2003, 12:59 AM
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The only 20W-50 that is diesel rated, that I know of, is Amsoil's synthetic:
http://www.amsoil.com/products/aro.html Red Line may also make a diesel-rated synthetic 20W-50. However there are no dino 20W-50 diesel oils that I am aware of. If someone finds one (not an ancient bottle, please), kindly post here and let us know what it is! Regards,
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