The task to refresh the engine oil of BK02837 and submission of an used oil sample for analysis was open for quite some time, but finally addressed on the eighth of June 2015. For reference, the total history of the oil-changes performed are listed below:
20150608 (191568km): Oil-service with Castrol Edge Professional TWS
20080910 (186108km): Oil-service with Castrol TWS Motorsport
20070507 (178717km): Oil-service with Castrol TWS Motorsport
20060506 (172777km): Oil-service with Castrol TWS Motorsport
20050408 (166715km): Oil-service with Castrol TWS Motorsport
20040508 (161621km): Oil-service with Castrol TWS Motorsport
20030603 (152746km): Oil-service with Castrol TWS Motorsport
20020404 (145393km): Oil-service with Castrol TWS Motorsport
20000907 (132236km): Oil-service with Castrol Formula SAE RS 10W60
20000316 (120504km): Oil-service with Castrol Formula SAE RS 10W60
19990914 (116206km): Oil-service with Shell Helix 5W40 (main dealer)
19990412 (103000km): Oil-service with Mobil1 at delivery
Apart from the earlier years (1999-2002) and 2003 (8800km), the replacement intervals are all lower than 7400k km and no more than one driving season apart. The tested sample started its service life in September 2008. By October 2009, BK02837 was put in long term storage at 191119km. The oil service was carried out in June 2015 at 191569km, the difference of which is explained by two single trips to warm-up the car before taking an oil sample. Although the distance covered with this oil-fill has been small (5460km), the total service life has been rather long (6,5 years). The purpose of the UOA at Blackstone is to get answers on the following questions.
1: What is the (baseline) condition of the engine after 191568km?
2: What is the amount of anti-wear additive present in the sample?
3: What is the quality of the engine oil after such a long period of inactivity?
When one takes a look at the properties that Blackstone measured, there is no reason to doubt the quality of the engine oil itself, not even after six-and a halve years. The viscosity is still within its range, meaning that the polymer chains needed for achieving its multi-grade specifications have not break down at all. In addition, the Total Base Number still is at a comfortable 5,3 (down from 8 ), meaning that there is plenty of active additive left before the oil becomes abrasive.
The level of anti-wear protection (ZDDP) was higher than expected for Castrol TWS Motorsport. However, since this sample dates back to 2008 it should be placed earlier in the time line for ZDDP trending data when Castrol still supplied the API SF/CJ grade Castrol TWS Motorsport. This sample is in line with other available UOA’s from the 2008-2011 timeline.
Please note that it is impossible to determine from UOA’s how far the ZDDP package has depleted. This is not possible with standard UOA-techniques. UOA’s however do show the content of the individual elements and thus one can use the results to compare with the manufacturers specifications of either one of its elements, zinc or phosphorus.
As for the condition of the engine, there are two benchmark references to compare with.
The first is GD55450, a 1992 E34 M5 from a good friend of mine. Its last UOA, refer to
post #44 revealed elevated copper-wear, but to an amount that one may consider as normal for an engine that has covered more than 310000km. During discussions with him, we discussed possible preventive measures to extend longevity of the engine, one of which is the pre-emptive replacement of piston-rod bearings, but it is hard to make such a decision without factual data. I honestly expected that his car would need such a measure first because of its high mileage. I didn’t expect that with my car with ‘just’ 191k km (120k miles).
The second is Anri’s textbook example of bearing wear, refer to
post 142. If one looks closely, Both reports have a striking resemblance for the wear related elements. The only differences are (1) Anri’s case is an S54B32 and not an S38B36 and (2) Anri’s report showed higher levels of Iron and lead.
This was not really expected for BK02837 because unlike GD55450, its mileage is still relatively low (less than 120k miles) and there are not much documented cases about S38B36’s with bearing wear. However GD55450 has seen more moderate use than BK02837 throughout the years. The many Alps tours with the E34 M5 community, the extensive use on the German autobahns and the circa one hundred Nordschleife laps probably have taken their toll.
It is nice to have a factual UOA to plan preventive actions. I already had planned for a preventive bearing replacement for BK02837, but I wanted at least two UOA’s first, hence why I will follow Blackstone’s advice to reduce the monitoring interval. This also allows me to quickly exhaust my existing stock of Castrol Edge Professional TWS before replacing the sump gasket that needs to be done also. This is an excellent opportunity to replace the bearing-shells at the same time.