I live in Canada and noticed something funny (not so funny in fact...), in the maintenance guide with imperial unit they recomend 5000 milles, and in the canadian one they recomend 5000 kilometer, 5000 milles is 8000 Km.. so they seem to be asking canadian customer to change oil more often! and this apply to the whole maintenance schedule! back on topic, I use full synth and change between 5000 and 7000 km usually... I noticed the car run smoother on synth