Just hit 6000 miles and changed the oil to 0w20 Magnatec. I've never really used castrol much but it was on sale and the regular price is around 21 dollars or so at walmart. I've heard rumors that Subaru's can be a little bit picky about oil especially M1. I bought this car new and plan on keeping it as long as it stays reliable so I want to use a quality oil and I'm willing to spend a little more if the oil really is better. I don't have much experience with boxer engines so any advice is appreciated.