Mobil 1 Extended Performance Motor Oil

I have been using Mobil 1 synthetic oil since 1994 on all of my vehicles that I have owned. I am a firm believer in synthetic oils. This extended performance oil really does what Mobil says. You can take the oil up to about 15,000 miles on oil changes. I work for CAT and can use their oil labs to have my oil tested. I use Mobil high efficiency oil filters and have tested my oil at 8,000 10,000 & 12,000 & 15,000 miles. This Mobil oil does still protect and not break down like conventional motor oils. If driving normally with your vehicle, you can go to 15,000 miles. If using this oil in severe driving conditions though, I have found that oil change intervals SHOULD be around 10,000 with a max of 12,000 miles. My brother delivered pizza for a year, and I tested his oil as well.