what's your experience on different brand of readily available 5w-30 (< $30 for 5 quarts) that has best wear protection? engine is a 4 banger, 2.0L. naturally aspirated. reason I am asking is that i saw, through the oil filling port, the wear mark on the nose of the cam lobe. rest of the lobe surface is OK. car has 15K miles on it. i've been using 5w-20. dealer did change except for the last one when i used conventional pennz. 5w-20. I really wanted to try 5w-30 (which is acceptible by the user manual) for better wear, but could not decide which brand to go with. please help.