How can I improve the gas mileage in my Vauxhall Vivaro?

I've noticed that my Vauxhall Vivaro is not getting as good gas mileage as it used to. What can I do to improve its fuel efficiency?

Regularly check and change your air filter to improve air flow and increase fuel efficiency.

Make sure your tires are properly inflated to reduce rolling resistance and improve gas mileage.

Avoid idling for long periods of time and combine errands to limit unnecessary trips.

Consider using a fuel additive to clean your engine and improve fuel efficiency.