Just got back from a long road haul with the Potiac Wave which is a Canadian second version of the Chev Aveo.

2005 Wave Hatchback
52000kms
Synthetic 0w30
Shell V-Power Premium Fuel

Over 622kms - Two 311km trips.

Avg each way: 34.7MPG

Even though I thought theat premium didn't make a difference, it definitely does with this car.

City economy jumped 2.7MPG with premium as well.

Testing done over 1 year.