Well i changed my oil bc its winter time, went from 20w50 and i put some thinner stuff in, i believe 10w30. Well anyways i drove it for 3 days no problems. I then took a 3 day vacation(not in truck). I came back today and started it up. ANyways, something sounds horrible, sounds like something is rattling around in motor and white smoke is coming outof the exhaust. I only had it runnin for like a min and it kept doin this. What is going on, any help wouldbe appreciated. Is it something as simple as oilin being to light? or something more serious?