BBC has been running fine for over a year using Shell Rotella oil and standard Wix filters. I was going on a 500 mile round trip last weekend so I decided to change the oil. Typically I have oil and filters here that is ordered from Summit but let my supply run out. While oil was draining, I drove over to Advance Auto to pick up oil and filter. They only had one 5 gallon jug of Shell ( I need 7 qts because of the pan)and no qt's so I used Royal Purple 15-40 which I thought was a good substitute. No Wix filters so I substituted it for a K&N. 100 miles into the trip I lost a lobe on number 4 cylinder and partial on number 7. I'm confused on what could have caused this. Never a problem out of this engine. The non roller cam is part of the Edelbrock top end kit that has been on this car for well over a year and well into 5000 miles. Sorta confused over this. 2 lobes!!