I see this a lot on those engines that come through the shop. Never understood why but it must not be bothersome because they seem to rack up a lot of miles without any trouble. Engine must be pretty gunked up, and you made a good choice in oil to clean it all up! It should improve every oil change from here on.
2004 Toyota Tacoma 3.4 V6: Pennzoil Platinum 5W-30
1997 Ford F-250HD 7.3 Powerstroke: Rotella T6 5W-40
1969 Ford Mustang Mach 1: 5.8 V8: PYB 10W-30