Was curious how long Rotella T6 could go between oil changes in my 1990 Craftsman GT6000 with an 18hp Briggs and Stratton opposed twin. Last July I changed it with Rotella T6 5W-40. I used it for mowing in summer and fall and plowing during the winter and the oil is still as clean as the day it was put in and haven't had to add any, oil currently has about 50 hours on it. Thanks