It could be a worn out engine, or like a 93 ranger I had,it used lots of oil and didn't smoke at all.The engine had 120 thousand miles and it had a burnt valve on the left head and then the right head blew a head gasket.I found a set of new heads cheap and that engine quit using oil and ran like new.So some times it is worth doing a valve job when a engine is using too much oil.Hope this helps you,good luck
