Why is the MPG of my Ford S-Max decreasing?

I've noticed that the fuel efficiency of my Ford S-Max has been steadily decreasing over the past few months. It used to get around 30 MPG, but now it's only getting around 25 MPG. What could be causing this and how can I improve it?

One possible reason for this decrease in MPG could be that your air filter or fuel filter is clogged. This can result in less air or fuel getting into the engine, causing it to run less efficiently. I would recommend getting these filters checked and replaced if necessary.

Another potential cause could be underinflated tires. When your tires are not properly inflated, it can create more drag on the road and cause your car to use more fuel. Make sure to check your tire pressure regularly and inflate them to the recommended level.

It's also possible that your car's spark plugs need to be replaced. If they are worn out, they can cause your engine to misfire and use more fuel. I suggest having a mechanic inspect and replace them if needed.