HelloCustomer mixing conventional oil and synthetical will have no detrimental effect at all. You can switch back and forth if you wanted to and would have no negative issues at all. If you run extended oil change intervals, that would be the only reservation. I wouldn't run that conventional oil for 5000 miles, but if you are running normal 3000 miles ranges, go ahead and don't worry at all. You will not hurt a single thing.
Your JA Expert,