Short story: Wifes Equinox burns oil... Using Castrol GTX Magnatec i have the consumption down to about a half quart a week give or take. Should I continue and change at the intended 5k mile mark? Or is it safe to say i can take it past knowing its getting a splash of fresh oil weekly. Also, I am using Napa Gold filter cartridges, how long are they good for realistically? Whats a safe milage for both? Thanks.