What is the best way to maintain the fuel efficiency in my Vauxhall Grandland?

I have noticed that my Vauxhall Grandland's fuel efficiency has decreased in the past few months. What steps can I take to improve it and keep it consistent?

Regularly check and change your air filter. This can improve fuel efficiency by up to 15%. Maddie, make sure to check your air filter every 12,000 miles.

Maintain proper tire pressure. Under-inflated tires can decrease fuel efficiency by 0.2% for every 1psi drop in pressure. Maddie, check your tire pressure at least once a month.

Avoid idling for long periods of time. Idling can use up to a gallon of fuel every hour. Maddie, turn off your engine if you anticipate being parked for more than 30 seconds.