[Michael Glover]

Amsoil lifetime filters are pretty good too and even less restrictive than K & N (apparently; according to Amsoil).
Also:
Change to synthetic oils (engine, gearbox and differential) will give a significant increase in power. I'm not really into Amsoil, but their oil seems to do the business.
Don't be hoodwinked into this extended oil drain interval/micro-filtration bullshit...it doesn't work and Amsoil's warranty, at the end of the day, isn't worth the paper it's written on. Been there and done that.
Run synthetic oil for 10,000 Km (6,000 miles) and change the filter at 5,000 Km (3,000 miles) and top-up the oil. Do this and the engine will last indefinately.
Always service the auto transmission at 20,000 km (12,000 miles)... get the bands adjusted and the filter and ATF replaced and the transmission will last indefinately. Amsoils synthetic ATF seems to be good in so much it is not affected by heat like mineral oil based ATF. Mobil have synthetic ATF too.
Replace the diff oil with Amsoil Series 2000 GL5 synthetic gear oil and the oil will never need replacing (unless it has water or something like that in it or has to be stripped down for repair, for some reason). Shell has synthetic gear oil as well.
Disclosure:
I'm not involved in any way with Amsoil and using their products in extended oil drain intervals, cost me two engines. Extended oil drain is not a good idea and the National Service Manager for Subaru New Zealand, was horrified at the notion. Amsoil declined to honour their warranty.