What is the best fuel-efficient engine for a Ford Focus?

I'm looking to improve the fuel efficiency of my Ford Focus, but I'm not sure which engine to choose. Which engine would you recommend for the best fuel efficiency?

Based on my personal experience, I would recommend the EcoBoost engine for the Ford Focus. It offers a great balance of power and fuel efficiency.

I have found that the diesel engine for the Ford Focus is the most fuel-efficient option. It may be more expensive upfront, but it will save you money in the long run.