case 1845 diesel motor

I have been using my 1845 case skidloader. put 20 hours or so on it last couple weeks. oil level is staying put but I notice I do get some light blue smoke out the exhaust. I believe its a 188 diesel motor. it starts and runs great. suspect it has been overhauled before I got it. just was wondering about the smoke. thought some of you diesel mechanics might give me some input. thanks norm

case 1845 diesel motor