2009 g6 2.4

Greetings all.
recently purchased a 2009 g6 with the 2.4. 43,000 miles This car is rated for 43 mpg Canadian . I figure I`d be happy with 38 to 40. This thing is lucky to see 30 mpg . Not impressed. I have a `03 Buick Century with 140,000 miles that gets better mileage and it still has original plugs . rant over .
The air filter on g6 is fairly clean . I was told fuel filter is in the fuel tank !! . has anyone swapped out the original plugs in these 4 bangers. What else can I do to get mileage up . Tires are up and no mil light showing . Or is the best these cars do !

Thanks Muff

I don't know what mpg Canadian means.....

here in the USA, it gets 22/33(26) for 6 speed auto.....22/30(25) for 4 speed auto.....city/hway(combined)....87 octane......

Easy to replace the plugs, take the ignition module off the top of the engine, plugs underneath.....

The Canadian gallon is equal to 4.54 litres of fuel where as the US gallon is 3.785 Litres of fuel .
Our gal is bigger and so the mileage should be better . Forgot to mention it is the 4 speed auto .

what plugs would you recommend ? is the fuel filter actually in fuel tank ?

What else can be done to tune thes ecars up