The initial focus of Formula 1's radical new era was always going to be about the engines.
With new 1.6-litre turbo regulations arriving to shake up the sport and kick it towards a more relevant future, work done by Renault, Ferrari and Mercedes was quite rightly going to have the biggest impact on the outcome of the championship.
But as the races have developed, and the strengths/weaknesses of the car packages have been exposed, there's an intriguing new battleground opening up in F1: fuel.