I have been reading this website for a week straight! Ok, Lets cut to the chase. Say for the sake of argument everybody here has an '02 jeep wrangler with the 4.0 inline 6. Jeep has 15k on it and is already on it's 3rd air filter! Jeep recomends only 10w-30. You live in the desert on a dusty dirt road. You change your oil and filter every 2500 miles due to the conditions. You cant see running any oil even synthetic over 3k due to the dust. It's 110 deg in the shade. Your dino choices are. Pennz, QS, havoline, Mobile, Castrol, Valvoline, Motorcraft, Coastal and Wallmarts tech 2000. What oil would you use and why?