i went to the auto store today and looked at oil prices. i noticed that penz is about 1.79 per quart and castrol like 1.85 per quart. then i looked at my oil mobil drive clean for 1.27. mobil super syn is about 3.75 or so. i noticed that i guess the better the oil the more expensive...then why is mobil cheaper....is there something wrong with mobil drive clean 10w30?