Thanks for the info StuntBikeJake, I did change my filters as recommended by the MTCE sched but low and behold as you stated they were no way ready to be changed. They were slightly dirty from doing their job but otherwise still extermely functional. I will in future first inspect them at the required interval and then decide to change if need be. I presume they will last a long time and may even be able to wash them, although the material is not thick and may tear easily. Either way this info will save me a lots of money as it is ridiculous the price they charge for those things....Thank all for the info... :)