Improvement on oil burning

So a little history, my 2006 Prius with 153000 miles has been burning oil consistently about 1qt every 1200 miles. The oil that I've used has been a 76 synthetic blend. This past time, I've gotten some mobil 1 5w30 with a rebate so I tried it (I thought it would be a big waste since the car burns so much oil).

To my surprise, the mobil 1 5w-30 is a lot more stable in the car, the car burns it at a much lower rate. I was able to go 2400 miles before adding the quart of oil, double the mileage of what I was getting with synthetic blend oil. I'm not sure what's the reason behind this as I always thought oils were quite similar, especially if you change it out at 5000 miles.

 

I've never used high mileage oils. I always thought those oils were just oil companies marketing a new name for the same product.