Why did low oil pressure light come on after oil change on 1982 Cadillac eldorado Changed oil and put in 4 qts of 10W40 and 1 qt slick 50 Just purchased car and have had no problems till oil change?

if there are no unusual noises coming from your engine, it may just be a bad sensor.(if theres no noise in engine there's proper lub). You may want to read this. http://www.ftc.gov/opa/1996/07/slick.shtm I have spoken tomechanics that have seen Slick 50 still in the bottom of the oil pan too thick to be pumped by the oil pump. Good luck.