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Apr 5, 2004
Atlanta, GA
I had Blackstone perform a UOA on a BMW 740il with 35K miles on the engine and 10k miles on the oil. The oil had been last changed 11 months ago at the BMW dealer, and I assume that it had BMW Long Life oil in it. I don't want to type in all the numbers but Blackstone writes "universal averages show typical wear from this type of engine after about 4,400 miles on the oil. Most of your wear looks okay, though lead, from bearings, read a bit on the high side [30 ppm]. When we have established wear trend from two or three samples, we'll know better whether this indicates a problem. It could be coming from an additive, or a temporary particle streak, and if so, may decline in the next sample. The TBN was low at 0.7 and the viscosity was high [sus viscosity @ 210 F = 79.8], so the oil was pretty well used up." Any comments?
I would not be surprised if the oil your dealer used turned out to be some dino oil or maybe a cheap blend. Any half-decent synthetic should show a better TBN after 10,000 miles. Dealers have been known to use the cheapest stuff available.
I think you're right about the BMW synthetic 5W30. I found 3 UOA's on BMW's using that oil. ...330i with 8,500 miles on the oil--TBN of 1.0 ...'99 M3 with 8,400 miles on the oil--TBN of 0.3 ...'03 325i with 7,700 mi. on oil--TBN of 2.3 From this, we can conclude that this oil is probably on its last gasp by 10K miles. 8K would be a much safer oil change interval. What we don't have in the UOA database are a lot of BMW V8's. There was 1 of a 1994 540i using Amsoil 10W40 for 2,000 miles. The lead wear was 6 ppm or 3 ppm/1K miles (which is where yours was at). Inline sixes might exhibit lower wear given their inherent balance. And, a lot depends on your driving habits. My family has two BMW's--a '95 525iT and a '97 328i. My most recent UOA's showed lead at 2 ppm over 7,300 miles, and 0 ppm over 4,200 miles. The first was on the older car using Schaeffer's 15W40. The second was on the other car using Chevron 10W40. Keep doing the UOA's until you've built up enough data on how your car can perform--and keep us informed!
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