I just purchased a 2002 Volvo CX70 (turbo). The oil filler hole is fill of black sludge that can't removed with a shop rag. I've seen a car with this much hard black sludge. I understand this common with Volvos. The car does not require synthetic oil. I' m using Pennzoil Ultra. But will use Castrol for RX treatment. What are your recommendations in this case? FYI: I had two semesters of orangic chemistry. training in industrial hydralic and tribology. My choice of oil filters is Mobil 1, theb Bosch. Your heip will be greatly appreciated.
Sorry to hear about the hardened sludge in the valve train under the oil filler cap. In some cases the amount of crusty build up under the filler cap is due to baffling, whereas only fumes can congedate around the filler hole. Hopefully the rest of the valve train is in better condition. Are there any other isswues such as oil consumption being excessive, or low oil pressure warning light on the dash board evident? Ordinarily we would recommend that you run two basic applications to remove hardened sludge deposits in a vehicle of this vintage. That would be running a full bottle of Auto-Rx with a fresh oil fill of conventional or group III synthetic oil, no group IV's. Then operate the vehicle for 3000 miles. I suggest changing out the filter at the 1500 mile mark to ensure good oil circulation. After finishing the 3000 miles run an oil change interval of 3000 milers with no Auto-Rx installed as a rinse phase. Then start the process all over again. If you are getting the warning lights on the dash board or are consuming alot of oil, then you may be a candidate for the fast track method of cleaning.
