Have done a very un-scientific test over the last 6 weeks and thought I would share my opinion with you all - it may or may not help? Ran my 2.5 auto for 3 weeks with a new OEM air filter and then for 3 weeks with a K&N filter. All journeys approx same distance (mainly motorway 200-300 trips) so the conditions were about the same for both tests. I know a lot of members run diesels so obviously no idea how this would compare. Conclusion of my test: didn't find any difference in power,performace,drivability, smoothness - nothing at all - both worked equally well. I am definately not an expert and would love to be enlighhtend by someone who knows but, if the air flow is increased with these filters surely the ECU would adjust the mixture (increasing fuel supply) so I cannot understand how it's claimed they can increase fuel consumption? I found no difference in my fuel consumption between the 2 filters and although the K&N is very well made and will probably out-live the car, I cannot see that it is worth paying the extra for one. As said, this is my opinion and I am by no way anti K&N - have used their induction kits in the past and they definately work (need a good cold air supply though) Maybe I have been unfair and need to run the tests for longer? Hope I have not offended anyone who has a K&N as it could just be me that doesn't see the benefit and theirs work well?