So my friends GMC motor home spun a rod bearing. He also noticed that mourning the oil pressure wasn't half way like normal but 1qtr up. As we where drivin down the road we suddenly heard a tapping and quickly shut the engine off. Checked oil, was good level but smelled burned. Had it towed home and two days later took oil filter apart to see black sludge. Date on can was july 2018. Only 2k on this oil. He was going to change the oil at the end of the month. So I guess do at least one year even if its not driving much. I did start it back with a new filter and oil pressure was normal but engine was tapping so hes looking to get it rebuild. 1975 GMC motor home olds 455. Some of the sludge eventually ran down after I took this picture.