I have had my 2004 XJ8 for about 5 years and have had to replace the air filter twice, a year apart. Is that normal & if so, how do I check to see if it is dirty?

 

You have to remove it to check, so I think it is on a 2-yearly replace cycle unless the car is used in a really dusty place. This assumes normal-type mileages. If the car only does a few miles a year why replace every two years ?

 

Remove filter and hold up in fairly dim light then place a torch against one side.

If you can see the torchlight then it's ok.

I don't replace filters, I just vacuum clean them but then I'm cheap lol.

 

Vacuum out the filter holder, esp. at the bottom. It collects a lot of debris, dust, leaves and such.