87' Chevy Blazer S-10, 6 cylinder, 140k miles

It could be eather the oil cooler lines or the oil filter adaptor. My dealer just had to replace both of these (at the same time)(just bought it last week).A friend of mine that does auto work also replaced the lines on another blazer a few days ago and he paid in the $125.-$140. Range for them. As for cost to install, id say<$75. As for the oil filter adaptor ive been told by another friend that spent 10 yrs at a gm dealer they are "known" for going out and are pretty cheap and easy to replace.I dont know how much they are but as far as instalation $35. Should do it. Good luck