Monday, April 13, 2015
Oil Service and Analysis
I have in the recent past considered switching to 15W-50 to compensate for the wider clearances in this aging engine but as I knew changing oils would diminish the significance of the oil analysis trend data I accumulated over the last several years I decided to continue using the same oil. This explains why I've been consistently buying BMW 5W-30, traditionally made by Castrol and provided in black bottles.
When I stopped by the dealer to pick up an oil service kit the parts guys gave me a new BMW branded oil that is provided in blue bottles and apparently made by Shell in the US. I suppose the good news is that since BMW has decided to change oil formulations and I'm planning to pull the engine anyway I can change oil brands / viscosity in the future.
Last weekend I got around to doing an overdue oil service and everything went as planned. I took an oil sample and received the results today. While not exactly unexpected, the news isn't particularly good. Normalized for the slightly extended oil service interval (6184 miles) lead is actually down somewhat from 0.0042 PPM per mile to 24 PPM / 6184 or 0.0038 PPM per mile. That's in the noise, statistically speaking, so it's safe to say lead is more or less the same. The real news, however, is that aluminum has doubled from a consistent 3 to 6 PPM (100% increase) and iron has risen substantially from 7 to 18 PPM (157% increase).
I expected to see some other elements from the bearings first but I'll take this as confirmation of what I already assumed...the engine is slowly beating itself to death and it's only a matter of time until something bad happens. It needs to be rebuilt.