Changed the oil early in Dec. 2018 with Castrol Edge 0W-40 and drove 10,000 miles in 9 months. My driving consists of an ordinary mix of short-tripping (between home and gym), commuting (14 miles each way) and highway driving (3 day-long trips). VW recommends a 10K OCI with a VW502 spec oil. I wondered how suitable this interval was for my situation and sent a sample to Blackstone Lab. The results are unremarkable and show that the 10K mile OCI was reasonable - at least for my driving style.
A few observations:
1. The 1.8L engine holds 6.7 quarts of oil, so there is plenty of additive reserve and capacity to hold contaminants in suspension over the full interval. This probably explains why adequate TBN (3.3) remained at the end, and the insoluble contamination was modest (0.8%). However, if my engine held only 4 quarts, I'm not so sure the results would be as good.
2. The viscosity at 100C declined to 10.7 cSt, which is in the middle of the SAE 30 range (9.3-12.5). Per the Castrol spec the viscosity of new Edge 0W-40 oil is 13.2 cSt. Clearly this version of Edge is not as robust to viscosity breakdown as Edge 5W-30, which Castrol claims is "3x stronger than the leading full synthetic against viscosity breakdown". Nevertheless, SAE 30 is certainly acceptable, and xW-30 oils are marketed which meet the VW502 spec. So, for my ordinary driving the partial loss viscosity is not too concerning.
3. I don't have a sense for the significance of the iron level at 27 ppm. As the lab commented, iron increases as the drain interval is extended. Is there another oil out there that produces a lower iron level for the same OCI?
A few observations:
1. The 1.8L engine holds 6.7 quarts of oil, so there is plenty of additive reserve and capacity to hold contaminants in suspension over the full interval. This probably explains why adequate TBN (3.3) remained at the end, and the insoluble contamination was modest (0.8%). However, if my engine held only 4 quarts, I'm not so sure the results would be as good.
2. The viscosity at 100C declined to 10.7 cSt, which is in the middle of the SAE 30 range (9.3-12.5). Per the Castrol spec the viscosity of new Edge 0W-40 oil is 13.2 cSt. Clearly this version of Edge is not as robust to viscosity breakdown as Edge 5W-30, which Castrol claims is "3x stronger than the leading full synthetic against viscosity breakdown". Nevertheless, SAE 30 is certainly acceptable, and xW-30 oils are marketed which meet the VW502 spec. So, for my ordinary driving the partial loss viscosity is not too concerning.
3. I don't have a sense for the significance of the iron level at 27 ppm. As the lab commented, iron increases as the drain interval is extended. Is there another oil out there that produces a lower iron level for the same OCI?