I have been using Mobil 1 High Mileage which has 1200ppm and widely available at Walmart. Also keep an eye on Mobil's website as they always have cash back offers. Got my last two 5 quart jugs for $15 a piece.
Racing oils have higher concentrations but lack any detergent packages so it gets dirty quick and needs to be changed much sooner. Not meant for longevity.