My 2013 Silverado with a 5.3L, when the OLM gets below 10%, which is roughly 7500 miles, give or take. The 2006 Jeep Liberty diesel, 11,000 miles. The Detroit Series 60 in my semi, 22,500, which is 50% over normal OEM recommended drain interval on that engine. Thinking of going to 25K since samples look good. Detroit grants allowance over the standard Series 60 15K interval to 22,500 if a 93K218 spec'd oil is used. Mine meets that. Will run the next one to 25K and see how it looks.