How do I improve my Ford Focus' fuel efficiency?

I've been noticing that my Ford Focus' fuel consumption has been increasing lately. What can I do to improve my car's fuel efficiency?

Dave, have you tried checking your tire pressure? Under-inflated tires can decrease fuel efficiency. Make sure to keep them at the recommended pressure.

Hi Dave, another quick tip is to avoid idling your car for too long. Turn off the engine if you're going to be parked for more than 30 seconds. This can save you gas in the long run.

Dave, have you changed your air filter recently? A dirty air filter can also contribute to decreased fuel efficiency. Make sure to replace it regularly.