I swear by K&N air filters. They are in everything I own (98 Corolla,
01 Prelude, 88 Delta 88,) plus every family members car I can get them in
(01 Saturn SL1, 02 Kia Sedona, 97 Tercel.) I find that depending on
application, they can improve throttle response (Kia, Olds) , top end power
(Prelude, Corolla), and fuel economy (Tercel, Saturn), or a combination of
all three. The K&N oil filters I don't find to be as good of a deal. You
won't see any performance / fuel economy increase with an oil filter. I
usually use WIX or UAP (made by WIX) oil filters as I find them to be a good
quality filter at about half the cost of the dealer, and about one quarter
the cost of a K&N. Personally, I believe in using a higher quality oil. I
change the oil and filters in the cars every 5000kms/3 months and because of
the extreme cold here in Canada (it's -20C or 4F today) I use 100% synthetic
oil (Mobil 1) in the Prelude, Corolla and Tercel and a synthetic blend in
the rest. As far as prices go, that obviously varies with application and
store but I found most of my filters in the $40.00 - $60.00 range. With the
Canadian dollar trading almost 1 to 1 with the Australian dollar, I'd expect
prices to be comparable.
Hope this helps,
Rob