i work for a body shop, and theres a service shop connected to it, i was talkin to a mechanic about me needing to change my oil and he said that he runs 15w 40 in his explorer, and my boss runs the same in his jeep and another guy in his dodge 1500. because of how thick and lubricating it is, also quiets down engine noise. im no mechanic so i want to no if this is SAFE, if it will cause immediate damage, or long term rotting on any seals or ANYTHING like that. am holding off on an oil change until i learn more. i don't want to put anything harmful in my truck. its a 95 f150 xl. 4.9l auto