Originally Posted By: GearheadTool
Assume I DID buy two bottles of Auto-RX, to go in the Volvo. (And I ignore the horror stories of it on a Subaru, and assume it will work well.) I have 80% conventional oil in there at the moment. How would I dose it? (How much bottle per mileage, etc?) Thanks!
Volvo are very specific in their advice about sludge and they states NO ADDITIVES.
If you do have a sludged engine then it needs to be cleaned top and bottom if bad, but in a moderate case just dropping the pan and cleaning it out and the screen to the oil pump in particular might suffice. Never use sludge removers that you drive around with as the risk of blocking the oil pump intake or turbo feed line is too high. If you must use a flush then the type designed to be used at idle for 10 minutes before an oil change are fairly safe, but watch the low oil pressure warning light just in case. Liqui Moly (Lubro Moly) flush seems good if you want a recommendation.
After cleaning the engine switch to an oil with a lot of Calcium based detergent content, like the top quality full synthetics and HM oils. Change oil and filter after a few thousand miles only as a precaution, particularly if the oil turns black very quickly.