some ?\'s about oil change.. ive only done it a few times so bair with me lol.. i dunno what kind of oil is in my truck cuase i havnt changed it since i got it...dont worry...ive only had it a couple months..lol. does 5 quarts of oil sound about right for a change? and would it be ok to put in a different kind of oil..than whats already in there? i was thinking about the quaker state 4x4 syn. blend..?