I have a K&N in my fiance's Mazda 6 and its got 25k on it and isn't that dirty after all these miles but plan on cleaning it soon. The filters are designed to work when their dirty due to the cotton gauze and special oil. The cost of a K&N is cheap when you consider the price of most replacement filters, let them go about 30k or more and you save even more!
I wouldn't stop at 30K. Sure, make SURE you clean them well every 30K (
and I think that's what you were saying), yet you NEVER need to replace them.
What im saying is I have a 2004 audi that is 9 years old and around 26,000 miles. I have never replaced the filter and I think its eating into my mpg a considerable amount . I have seen the computer say 11 mpg , but I think that was because I was idiling and not being eco friendly with the gas pedal (speed demon) =) . Since I am younger and I dont have the time to re oil a k and n. I will be using the mann filter for my vehicle. I think it would be my best option as its cheap and effective.
Bill, I think you should replace ANY filter of OEM/paper design that's that old, no matter the mileage. Simply put, putting paper through that many heat cycles, weather SEASONS, will make the paper deterioate.
As has been said (and really would need to study why it was said) these days with computer controlled engine management systems MAF and MAP sensors and the like, a clogged filter generally doesn't hurt mileage but it WILL hurt horsepower. The computer sees that there is less air in the intake side of the engine and just doesn't allow the same amount of fuel to be deposited into the combustion side of the system.
That being said, a compromised filter will allow dirty air to enter the system which can affect performance of multiple sensors, sometimes to the point where the sensors will fail, as well as accellerate internal wear of the valvetrain, cylinders, pistons, rings, even the bottom end of the engine. So YES replacing a air filter is the cheapest thing you can do, followed by an oil change, to help protect your engine. :dblthumb2:
Apparently I'm in the minority in this thread, but I don't think that by changing your air filter is going to improve your mileage, I can't even see it being that dirty unless you drive on dirt roads or you have a lot more time on that engine than 26K miles would indicate.
Again, with a current tech car with a MAF sensor, a clogged air filter will not result in reduced mileage, it will result in reduced power; the computer is only going to inject the proper amount of fuel for the air mass being introduced. This was not the case back in the old carburetor days when a clogged air filter could affect your fuel mixture.
PS When you are idling you get 0 MPG.
Hope I addressed that above.
I the 9 years I have gotten some oil changes, new brakes, new windshield wipers and other very small parts. I have never gotten plugs or wires replaced
FWIW, a 2004 is actually 10 years old now as the 2013's have been rolled out you count them too.
I don't know if it really needs wires with only that many miles on it. Depends more on how it's been kept, garaged full time or not. The weather plays a big part in how rubber and plastic break down over the years.
It may not hurt to look into replacing the wires and while the plugs (should) be fine with that many years on them, if you're doing the wires it's not that hard and only like $6 a piece to replace them.
Sounds like the car surely doesn't get driven much, even less than my G35 which is a 2006 and just turned 29K last week. It has only been in TWO rainstorms and in any rain at all (
including a passing sprinkle) 7 times since new. Mine is a garage queen and even with 29K I don't even consider changing plugs and wires. (not yet)
But.... my climate is fairly mild and as I mentioned, garaged full time. If you are in the north where the temps swing wildly during the seasons, the car has been through a lot of weather and such, as the saying goes ymmv.
Hey Bill, I was young once and I freaking LOVED to spend everything I had on my cars to make more power from them. That's not so easy now as for the most part engines are tuned to the point where they are making as much power as possible from the factory. We used to change intake and carbs, or exhaust and headers, even drop in a new distributor and a high energy coil and make power. Now the first thing you can do is MAYBE go to a CAI system (which on some engines doesn't help at all). The only proven way to make power is with a turbo or supercharger. Next step would be to spring for new injectors and possibly a fuel rail and a bigger throttle body. All of those are terribly expensive,
but a LOT of fun! 
For what a turbo setup runs these days I could build a complete 450HP V8 in the 70's. Yet an OEM engine making that power now will get decent mileage, back then.... I got about 7 on a good day, 5 when lead footin' it (which was pretty much all day long). My Dad just never understood why when I was 19 I had 2 cars in the driveway, one that'd turn 10's all day, the other stock. And of course 2 streetbikes one for my girlfriend (now my wife) and another a Kaw Z-900 that I had no business with! :laughing:
Cardaddy
