I have always used Mobil 1, great oil, and you can get it cheap in 5qt jugs at Wal-Mart! fully synthetic is the way to go because it does not have the organic matrial in it that conventional or blended oil has, that organic material is the reason you have to change your oil, it is carbon, with Mobil 1, I change every 10,000-12,000 and don't even have to at that point, just comforting I guess. Unless you are in cold climate all the time, I would use 10w-50. because it is HOT in FL I use 20w-50 in the 98 Vette (even though they say to use 5w-20) and the Impala in the summer, and 10w-50 in winter. I have had a K & N in the Impala for 5 years, this is what I see as the benifit of the K&N, longevity, just clean it, soak it, and you are off, as for air flow, I may have seen a 1 to 2 mpg jump from the stock.