hello all i have a 93 explorer with the 4.0 and it runs really well and has alot of power and seems to have more power than my parents 96 explorer with the 4.0 but my question today it that i just bought it a couple of months ago and i had the oil changed in it after i got it and its nearing time for the next oil change and ive used 2 quarts and i cant figure out where its going..i changed the plugs...they were dry,the exhaust doesnt have any kind of oily film in it and it does not leak whats the deal ???