Could switching from Synthetic to Conventional cause oil to burn? 

I needed to top off my 2004 Prius. All I had was conventional 5W-30 on hand. It usually gets synthetic 0W-20. So I topped it off with the 5W-30. 

I noticed that after putting the 5W-30, it seemed to go through oil faster. Needing more top offs before an oil change. 

I got an oil change, and topping off with 0W-20. And while it still burns a little bit of oil, it’s not as much as when I was using 5W-30 to top off. 

Is my mind playing tricks on me, or can switching from synthetic 0W-20 to 5W-30 cause more oil burning?

*The updated specs says the Prius can take either oil.