Ok a dumb question. Just wondering if there is any thing wrong, if i mix different brand of oil for a oil change. Like i have 10w-40 2 quarts of penzoil and 10w-40 2 quarts of Mobile or does it not matter? as long as it is 10w-40 and its conventional oil. See i buy 5 quarts at a time and i only use 4 quarts, so after a while, i got all these bottles with different types of oil, and ther is no use for them.